Methods and systems for generating and rendering object based audio with conditional rendering metadata

ABSTRACT

Methods and audio processing units for generating an object based audio program including conditional rendering metadata corresponding to at least one object channel of the program, where the conditional rendering metadata is indicative of at least one rendering constraint, based on playback speaker array configuration, which applies to each corresponding object channel, and methods for rendering audio content determined by such a program, including by rendering content of at least one audio channel of the program in a manner compliant with each applicable rendering constraint in response to at least some of the conditional rendering metadata. Rendering of a selected mix of content of the program may provide an immersive experience.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/807,922, filed on Apr. 3, 2013,and the benefit of the filing date of U.S. Provisional PatentApplication No. 61/832,397, filed on Jun. 7, 2013.

TECHNICAL FIELD

The invention pertains to audio signal processing, and moreparticularly, to encoding, decoding, and interactive rendering of audiodata bitstreams which include audio content (indicative of at least onespeaker channel and at least one audio object channel), and metadatawhich supports conditional rendering of the audio content in a mannerdependent on playback speaker configuration. Some embodiments of theinvention generate, decode, and/or render audio data in one of theformats known as Dolby Digital (AC-3), Dolby Digital Plus (Enhanced AC-3or E-AC-3), or Dolby E.

BACKGROUND OF THE INVENTION

Dolby, Dolby Digital, Dolby Digital Plus, and Dolby E are trademarks ofDolby Laboratories Licensing Corporation. Dolby Laboratories providesproprietary implementations of AC-3 and E-AC-3 known as Dolby Digitaland Dolby Digital Plus, respectively.

Although the invention is not limited to use in encoding audio data inaccordance with the E-AC-3 (or AC-3 or Dolby E) format, or delivering,decoding or rendering E-AC-3, AC-3, or Dolby E encoded data, forconvenience it will be described in embodiments in which it encodes anaudio bitstream in accordance with the E-AC-3 or AC-3 or Dolby E format,and delivers, decodes, and renders such a bitstream.

A typical stream of audio data includes both audio content (e.g., one ormore channels of audio content) and metadata indicative of at least onecharacteristic of the audio content. For example, in an AC-3 bitstreamthere are several audio metadata parameters that are specificallyintended for use in changing the sound of the program delivered to alistening environment.

An AC-3 or E-AC-3 encoded bitstream comprises metadata and can compriseone to six channels of audio content. The audio content is audio datathat has been compressed using perceptual audio coding. Details of AC-3coding are well known and are set forth in many published referencesincluding the following:

ATSC Standard A52/A: Digital Audio Compression Standard (AC-3), RevisionA, Advanced Television Systems Committee, 20 Aug. 2001; and

U.S. Pat. Nos. 5,583,962; 5,632,005; 5,633,981; 5,727,119; and6,021,386.

Details of Dolby Digital Plus (E-AC-3) coding are set forth in, forexample, “Introduction to Dolby Digital Plus, an Enhancement to theDolby Digital Coding System,” AES Convention Paper 6196, 117^(th) AESConvention, Oct. 28, 2004.

Details of Dolby E coding are set forth in “Efficient Bit Allocation,Quantization, and Coding in an Audio Distribution System”, AES Preprint5068, 107th AES Conference, August 1999 and “Professional Audio CoderOptimized for Use with Video”, AES Preprint 5033, 107th AES ConferenceAugust 1999.

Each frame of an AC-3 encoded audio bitstream contains audio content andmetadata for 1536 samples of digital audio. For a sampling rate of 48kHz, this represents 32 milliseconds of digital audio or a rate of 31.25frames per second of audio.

Each frame of an E-AC-3 encoded audio bitstream contains audio contentand metadata for 256, 512, 768 or 1536 samples of digital audio,depending on whether the frame contains one, two, three or six blocks ofaudio data respectively. For a sampling rate of 48 kHz, this represents5.333, 10.667, 16 or 32 milliseconds of digital audio respectively or arate of 189.9, 93.75, 62.5 or 31.25 frames per second of audiorespectively.

As indicated in FIG. 1, each AC-3 frame is divided into sections(segments), including: a Synchronization Information (SI) section whichcontains (as shown in FIG. 2) a synchronization word (SW) and the firstof two error correction words (CRC1); a Bitstream Information (BSI)section which contains most of the metadata; six Audio Blocks (AB0 toAB5) which contain data compressed audio content (and can also includemetadata); waste bits (W) which contain any unused bits left over afterthe audio content is compressed; an Auxiliary (AUX) information sectionwhich may contain more metadata; and the second of two error correctionwords (CRC2).

As indicated in FIG. 4, each E-AC-3 frame is divided into sections(segments), including: a Synchronization Information (SI) section whichcontains (as shown in FIG. 2) a synchronization word (SW); a BitstreamInformation (BSI) section which contains most of the metadata; betweenone and six Audio Blocks (AB0 to AB5) which contain data compressedaudio content (and can also include metadata); waste bits (W) whichcontain any unused bits left over after the audio content is compressed;an Auxiliary (AUX) information section which may contain more metadata;and an error correction word (CRC).

In an AC-3 (or E-AC-3) bitstream there are several audio metadataparameters that are specifically intended for use in changing the soundof the program delivered to a listening environment. One of the metadataparameters is the DIALNORM parameter, which is included in the BSIsegment.

As shown in FIG. 3, the BSI segment of an AC-3 frame (or an E-AC-3frame) includes a five-bit parameter (“DIALNORM”) indicating theDIALNORM value for the program. A five-bit parameter (“DIALNORM2”)indicating the DIALNORM value for a second audio program carried in thesame AC-3 frame is included if the audio coding mode (“acmod”) of theAC-3 frame is “0”, indicating that a dual-mono or “1+1” channelconfiguration is in use.

The BSI segment also includes a flag (“addbsie”) indicating the presence(or absence) of additional bit stream information following the“addbsie” bit, a parameter (“addbsil”) indicating the length of anyadditional bit stream information following the “addbsil” value, and upto 64 bits of additional bit stream information (“addbsi”) following the“addbsil” value.

The BSI segment includes other metadata values not specifically shown inFIG. 3.

It has been proposed to include metadata of other types in audiobitstreams. For example, methods and systems for generating, decoding,and processing audio bitstreams including metadata indicative of theprocessing state (e.g., the loudness processing state) andcharacteristics (e.g., loudness) of audio content are described in PCTInternational Application Publication Number WO 2012/075246 A2, havinginternational filing date Dec. 1, 2011, and assigned to the assignee ofthe present application. This reference also describes adaptiveprocessing of the audio content of the bitstreams using the metadata,and verification of validity of the loudness processing state andloudness of audio content of the bitstreams using the metadata.

Methods for generating and rendering object based audio programs arealso known. During generation of such programs, it may be assumed thatthe loudspeakers to be employed for rendering are located in arbitrarylocations in the playback environment (or that the speakers are in asymmetric configuration in a unit circle). It need not be assumed thatthe speakers are necessarily in a (nominally) horizontal plane or in anyother predetermined arrangements known at the time of programgeneration. Typically, metadata included in the program indicatesrendering parameters for rendering at least one object of the program atan apparent spatial location or along a trajectory (in a threedimensional volume), e.g., using a three-dimensional array of speakers.For example, an object channel of the program may have correspondingmetadata indicating a three-dimensional trajectory of apparent spatialpositions at which the object (indicated by the object channel) is to berendered. The trajectory may include a sequence of “floor” locations (inthe plane of a subset of speakers which are assumed to be located on thefloor, or in another horizontal plane, of the playback environment), anda sequence of “above-floor” locations (each determined by driving asubset of the speakers which are assumed to be located in at least oneother horizontal plane of the playback environment). Examples ofrendering of object based audio programs are described, for example, inPCT International Application No. PCT/US2001/028783, published underInternational Publication No. WO 2011/119401 A2 on Sep. 29, 2011, andassigned to the assignee of the present application.

Above-cited U.S. Provisional Patent Application No. 61/807,922 andabove-cited U.S. Provisional Patent Application No. 61/832,397 describeobject based audio programs which are rendered so as to provide animmersive, personalizable perception of the program's audio content. Thecontent may be indicative of the atmosphere at (i.e., sound occurring inor at) and/or commentary on a spectator event (e.g., a soccer or rugbygame, or another sporting event). The audio content of the program maybe indicative of multiple audio object channels (e.g., indicative ofuser-selectable objects or object sets, and typically also a default setof objects to be rendered in the absence of object selection by theuser) and at least one bed of speaker channels. The bed of speakerchannels may be a conventional mix (e.g., a 5.1 channel mix) of speakerchannels of a type that might be included in a conventional broadcastprogram which does not include an object channel.

Above-cited U.S. Provisional Patent Applications No. 61/807,922 and No.61/832,397 describe object related metadata delivered as part of anobject based audio program which provides mixing interactivity on theplayback side, including by allowing an end user to select a mix ofaudio content of the program for rendering, instead of merely allowingplayback of a pre-mixed soundfield. For example, a user may select amongrendering options provided by metadata of a typical embodiment of theinventive program to select a subset of available object channels forrendering, and optionally also the playback level of at least one audioobject (sound source) indicated by the object channel(s) to be rendered.The spatial location at which each selected sound source is rendered maybe predetermined by metadata included in the program, but in someembodiments can be selected by the user (e.g., subject to predeterminedrules or constraints). In some embodiments, metadata included in theprogram allows user selection from among a menu of rendering options(e.g., a small number of rendering options, for example, a “home teamcrowd noise” object, a “home team crowd noise” and a “home teamcommentary” object set, an “away team crowd noise” object, and an “awayteam crowd noise” and “away team commentary” object set). The menu maybe presented to the user by a user interface of a controller, and thecontroller may be coupled to a set top device (or other device)configured to decode and render (at least partially) the object basedprogram. Metadata included in the program may otherwise allow userselection from among a set of options as to which object(s) indicated bythe object channels should be rendered, and as to how the object(s) tobe rendered should be configured.

U.S. Provisional Patent Applications No. 61/807,922 and No. 61/832,397describe an object based audio program which is an encoded audiobitstream indicative of at least some of the program's audio content(e.g., a bed of speaker channels and at least some of the program'sobject channels) and object related metadata. At least one additionalbitstream or file may be indicative of some of the program's audiocontent (e.g., at least some of the object channels) and/or objectrelated metadata. In some embodiments, object related metadata providesa default mix of object content and bed (speaker channel) content, withdefault rendering parameters (e.g., default spatial locations ofrendered objects). In some embodiments, object related metadata providesa set of selectable “preset” mixes of object channel and speaker channelcontent, each preset mix having a predetermined set of renderingparameters (e.g., spatial locations of rendered objects). In someembodiments, object related metadata of a program (or a preconfigurationof the playback or rendering system, not indicated by metadata deliveredwith the program) provides constraints or conditions on selectable mixesof object channel and speaker channel content.

U.S. Provisional Patent Applications No. 61/807,922 and No. 61/832,397also describe an object based audio program including a set ofbitstreams (sometimes referred to as “substreams”) which are generatedand transmitted in parallel. Multiple decoders may be employed to decodethem (e.g., if the program includes multiple E-AC-3 substreams theplayback system may employ multiple E-AC-3 decoders to decode thesubstreams). Each substream may include synchronization words (e.g.,time codes) to allow the substreams to be synchronized or time alignedwith each other.

U.S. Provisional Patent Applications No. 61/807,922 and No. 61/832,397also describe an object based audio program which is or includes atleast one AC-3 (or E-AC-3) bitstream, and includes one or more datastructures referred to as containers. Each container which includesobject channel content (and/or object related metadata) is included inan auxdata field (e.g., the AUX segment shown in FIG. 1 or FIG. 4) atthe end of a frame of the bitstream, or in a “skip fields” segment ofthe bitstream. Also described is an object based audio program which isor includes a Dolby E bitstream, in which the object channel content andobject related metadata (e.g., each container of the program whichincludes object channel content and/or object related metadata) isincluded in bit locations of the Dolby E bitstream that conventionallydo not carry useful information. U.S. Provisional Application No.61/832,397 also describes an object based audio program including atleast one set of speaker channels, at least one object channel, andmetadata indicative of a layered graph (a layered “mix graph”)indicative of selectable mixes (e.g., all selectable mixes) of thespeaker channels and object channel(s). The mix graph may be indicativeof each rule applicable to selection of subsets of the speaker andobject channels, is indicative of nodes (each of which may be indicativeof a selectable channel or set of channels, or a category of selectablechannels or set of channels) and connections between the nodes (e.g.,control interfaces to the nodes and/or rules for selecting channels).The mix graph may indicate essential data (a “base” layer) and optionaldata (at least one “extension” layer), and where the mix graph isrepresentable as a tree graph, the base layer can be a branch (or two ormore branches) of the tree graph, and each extension layer can beanother branch (or set of branches) of the tree graph.

As noted, it has been proposed to include, in an object based audioprogram, object related metadata which indicates rendering parametersfor rendering at least one object (indicated by an object channel of theprogram) at an apparent spatial location or along an apparent trajectory(in a three dimensional volume) using an array of speakers. For example,an object channel of the program may have corresponding metadataindicating a three-dimensional trajectory of apparent spatial positionsat which the corresponding object is to be rendered. The trajectory mayinclude a sequence of “floor” locations in a “floor” plane (where the“floor” plane is a horizontal plane which nominally includes theexpected positions of the listener's ears) of the playback environment,and a sequence of “above-floor” locations above the floor plane. It hasbeen proposed to render an object of an object based program atabove-floor locations, including by generating at least one speaker feedfor driving at least one “above-floor” speaker (of a playback speakerarray) which is assumed to be located above the floor plane in theplayback environment. Such an above-floor speaker is sometimes referredto herein as a “height” speaker.

Traditionally, audio downmixing of a multi-channel audio program isperformed in accordance with a predetermined formula, to collapse(downmix) a first set of channels of the program (N channels indicativeof a first soundfield, where N is an integer) down to a second set ofchannels (M channels indicative of a downmixed soundfield, where M is aninteger less than N) for playback by an available speaker arraycomprising M speakers (e.g., a stereo television speaker arrayconsisting of two speakers). During playback after downmixing, theavailable speaker array emits sound indicative of the downmixedsoundfield. Typically, traditional downmixing of this type includes inthe second set of channels (i.e., the downmix) audio content of all thechannels in the first set.

If no above-floor (“height”) speaker is present in the playback systemspeaker array, a traditional downmixing technique (of the type mentionedabove) could be employed to downmix content of an object channel withcontent of speaker channels of the program (where the speaker channelcontent is intended to be played by floor speakers of the playbackspeaker array), so that the resulting downmixed sound is emitted onlyfrom floor speakers of the playback speaker array. However, theinventors have recognized that because the content of the above-floorobject channel would be downmixed into the content of the originalspeaker channels, the traditional downmixing would undesirably result incacophonous sound upon playback of the resulting downmix (e.g., theabove-floor content would be perceived as interfering with originalspeaker channel content).

The inventors have also recognized that a traditional downmixingtechnique (of the above-mentioned type) has other limitations anddisadvantages, not necessarily related to the presence or absence ofheight speakers in the playback speaker array. For example the inventorshave recognized that, even in traditional 5.1 channel audio production,compromises are often made to preserve a reasonable soundfield for astereo downmix. For example, a broadcaster may want to place acommentary (or other dialog element) in the surround channels of a 5.1channel program, but choose not to do so since a traditionallyimplemented stereo downmix of the desired representation does notprovide a pleasing or representative experience to stereo televisionviewers.

Until the present invention, it had not been known how to renderdownmixes of selected channels (e.g., object and speaker channels) of anobject based audio program, in a manner which ensures that the downmixesare compliant with predetermined downmixing constraints (e.g., one ormore downmixing constraints specified by the entity which generates andbroadcasts the program, or by the program content creator) based onplayback speaker array configuration (e.g., to avoid cacophonous orotherwise undesirable downmixed sound upon playback). Differentembodiments of the invention apply to any and all conditions where theprogram is indicative of more audio channels than those available in thefinal reproduction environment (i.e., all conditions in which theprogram includes more channels (object channels and/or speaker channels)than the number of speakers, of the playback speaker array, to bedriven).

BRIEF DESCRIPTION OF EMBODIMENTS OF THE INVENTION

A class of embodiments of the invention includes methods for generationand conditional rendering of interactive object based audio, based onplayback speaker array configuration (where playback speaker array“configuration” denotes in this context at least one configurationattribute, e.g., the number of speakers in the array and the actual orassumed placement of each speaker in the playback environment).

Object related metadata in an object based audio program (generated inaccordance with some embodiments of the invention) indicates renderingparameters for rendering at least one object (indicated by an objectchannel of the program) at an apparent spatial location, or along anapparent trajectory (in a three dimensional volume), using a playbacksystem speaker array. For example, an object channel of the program mayhave corresponding metadata indicating a three-dimensional trajectory ofapparent spatial positions at which the corresponding object is to berendered. The trajectory may include a sequence of “floor” locations(nominally in the plane of the floor of the playback environment, whichis assumed to coincide at least approximately with the horizontal planeof the listener's ears), and a sequence of “above-floor” locations abovethe floor plane. To render the object at above-floor locations, at leastone speaker feed is generated for driving at least one speaker of theplayback speaker array which is assumed to be located above the floorplane in the playback environment.

A class of embodiments comprises methods for generation and/or renderingof an object based audio program which includes conditional renderingmetadata corresponding to at least one object channel (e.g., anabove-floor object channel) of the program. Thus, each audio objectindicated by each such object channel has corresponding conditionalrendering metadata. For example, in some embodiments an audio objecthaving corresponding conditional rendering metadata may be anabove-floor object.

In a class of embodiments, the conditional rendering metadata is objectrelated metadata indicative of at least one rendering constraint, basedon playback speaker array configuration, which applies to eachcorresponding object channel (i.e., each object channel corresponding tothe conditional rendering metadata). An example of such a renderingconstraint is a prohibition against rendering a corresponding objectchannel when the playback speaker array configuration is of a specifictype. A playback system (having knowledge that its playback speakerarray is of this specific type) may be configured (e.g., preconfigured,or configured in response to metadata of the program) to operate inresponse to conditional rendering metadata indicative of such renderingconstraint by preventing implementation of rendering of content of theobject channel into a speaker feed (for use in driving a playbackspeaker). Another example of a rendering constraint indicated by theconditional rendering metadata generated (by a method in the class ofembodiments) is an indication of at least one permissible type ofrendering of content of a corresponding object channel when the playbackspeaker array configuration is of a specific type. Other examples ofrendering constraints indicated by conditional rendering metadata areindications of placement, level, size, and other attributes (e.g.,special effects processing to be performed on) with (or as to which)content of a corresponding object channel is included in each speakerfeed generated during rendering of the content, so that when therendered content is played by the playback speaker array it will beperceived as emitting from an apparent source (object) with the spatialposition, level, size, and/or other attributes indicated by themetadata.

In some embodiments, the conditional rendering metadata is objectrelated metadata indicative of at least one rendering restraint which isa downmixing constraint, based on playback speaker array configuration,which applies to each corresponding object channel (i.e., each objectchannel corresponding to the conditional rendering metadata). An exampleof such a downmixing constraint is a prohibition against downmixing of acorresponding object channel when the playback speaker arrayconfiguration is of a specific type. A playback system (having knowledgethat its playback speaker array is of this specific type) may beconfigured (e.g., preconfigured, or configured in response to metadataof the program) to operate in response to conditional rendering metadataindicative of such downmixing constraint by preventing implementation ofany downmix of the object channel into a speaker channel of the program.Another example of a downmixing constraint indicated by the conditionalrendering metadata generated (by a method in the class of embodiments)is an indication of at least one permissible downmix (or type ofdownmix) including a corresponding object channel when the playbackspeaker array configuration is of a specific type. Other examples ofdownmixing constraints indicated by conditional rendering metadata areindications of placement, level, size, and other attributes of (e.g.,special effects processing to be performed on) an audio object (in adownmix of the corresponding object channel into one or more speakerchannels) based on playback speaker configuration.

It should be appreciated that the expression “to perform a downmix” ofor on (or “to downmix” or to “render a downmix” of or on) N channels ofan object based audio program is used herein in a broad sense to denotedetermination or generation of M speaker feeds (indicative of content ofat least some, and typically all, of the N channels of the program) fordriving M speakers of a playback speaker array, where N is an integerand M is an integer less than N. In one example, conditional renderingmetadata which pertains to an object channel (of a program including Nchannels) is indicative of at least one downmixing constraint (based onplayback speaker array configuration) in the sense that a first subsetof the conditional rendering metadata indicates some attribute of (orrule pertaining to) the generation of M1 speaker feeds for driving afirst array of M1 playback speakers such that the M1 speaker feeds areindicative of a downmix of content of the program including content ofthe object channel, and a second subset of the conditional renderingmetadata indicates some attribute of (or rule pertaining to) generationof M2 speaker feeds for driving a different array of M2 playbackspeakers such that the M2 speaker feeds are indicative of anotherdownmix of content of the program including content of the objectchannel, where M1 is not equal to M2. In this example, rendering of adownmix on N channels of a program for playback by the first array of M1speakers would typically include steps of selecting the first subset ofthe conditional rendering metadata (rather than the second subset of theconditional rendering metadata) and using the selected first subset ofthe conditional rendering metadata to determine or generate theappropriate M1 speaker feeds.

In a class of embodiments, the invention is a method for generating anobject based audio program, said method including steps of:

generating conditional rendering metadata corresponding to at least oneobject channel, such that the conditional rendering metadata isindicative of at least one rendering constraint (e.g., a downmixingconstraint), based on playback speaker array configuration, whichapplies to said at least one object channel;

determining a set of audio channels including said at least one objectchannel (and optionally also at least one speaker channel); and

generating the object based audio program such that said object basedaudio program is indicative of the set of audio channels and theconditional rendering metadata, and such that content of at least oneaudio channel of the set of audio channels is renderable, in a mannercompliant with the at least one rendering constraint, by a playbacksystem in response to at least some of the conditional renderingmetadata.

Optionally, the conditional rendering metadata is also indicative of atleast one rendering rule (e.g., at least one downmix rule), based onplayback speaker array configuration, for rendering (e.g., implementinga downmix of) audio channels of the program. For example, theconditional rendering metadata may indicate the following rules:

each object channel of the program of a first type (e.g., as indicatedby at least some conditional rendering metadata of the program) shouldbe downmixed into any speaker channel specified by any user-selected (ordefault) mix of content of the program if the playback speaker arrayincludes at least one above-floor speaker,

each object channel of the program of the first type should be ignored(i.e., should not be included in any downmix) by the playback system ifthe playback speaker array does not include at least one above-floorspeaker, and

each object channel of the program of a second type (e.g., as indicatedby at least some conditional rendering metadata of the program) shouldbe downmixed into any speaker channel specified by any user-selected (ordefault) mix of content of channels of the program regardless ofconfiguration of the playback speaker array.

It is contemplated that generation of an object based audio program inaccordance with some embodiments of the invention includes a step ofselecting a subset of available (i.e., previously generated) conditionalrendering metadata and including the selected conditional renderingmetadata (but not unselected conditional rendering metadata) in theprogram.

In other embodiments, the invention is a method of rendering audiocontent determined by an object based audio program, wherein the programis indicative of conditional rendering metadata corresponding to atleast one object channel, and a set of audio channels including the atleast one object channel (and optionally also at least one speakerchannel), and wherein the conditional rendering metadata is indicativeof at least one rendering constraint (e.g., at least one downmixingconstraint), based on playback speaker array configuration, whichapplies to said at least one object channel, said method including stepsof:

(a) providing the object based audio program to an audio processingunit; and

(b) in the audio processing unit, parsing the conditional renderingmetadata and the set of audio channels, and rendering content of atleast one audio channel of the set of audio channels, in a mannercompliant with the at least one rendering constraint, in response to atleast some of the conditional rendering metadata.

In some such embodiments, the set of audio channels includes at leastone speaker channel, and step (b) includes a step of selecting at leastone object channel of the set of audio channels, and mixing eachselected object channel of the set with at least one speaker channel ofthe set to generate a downmix of content of said each selected objectchannel and the at least one speaker channel. Typically, the downmixconsists of a set of N downmixed speaker channels, where N is a positiveinteger, and step (b) includes a step of causing N speakers of aplayback speaker array to emit sound by driving the speakers withspeaker feeds generated from the downmixed speaker channels.

Optionally, the conditional rendering metadata is also indicative of atleast one rendering rule (e.g., at least one downmix rule), based onplayback speaker array configuration, and the rendering performed instep (b) is compliant with the rendering rule.

An object based audio program generated in accordance with typicalembodiments of the invention may be rendered to cause sound indicativeof downmixed content (e.g., of object channels and/or speaker channels)of the program played by a playback speaker array to be perceived asemitting from different apparent source locations within the soundreproduction (playback) environment. For an interactive presentation,objects determined by selected ones of selectable object channels arerendered at locations (e.g., a set of different static locations,corresponding to different ones of a set of selected objects) within therendered soundfield, such that audio content of each selected objectchannel is rendered so as to be perceived as emitting from an apparentsource location (or trajectory of locations) determined by objectrelated metadata corresponding to the selected object channel. Forexample, an immersive sound mix determined from an object based audioprogram may indicate sound which is in turn indicative of a “publicaddress” audio object (determined by a selected object channel of theprogram) so as to be perceived as emitting from an apparent sourcelocation above the assumed listener's position within the reproductionenvironment to give the listener (consumer) the experience of being in astadium while announcements are emitted from a public addressloudspeaker mounted above the listener. Such a public address audioobject may be selected for rendering and playback by a speaker arraycomprising at least one above-floor speaker physically located in ahorizontal plane (sometimes referred to as an “above-floor” or “height”plane) above a “floor” plane, where the “floor” plane is a horizontalplane which nominally includes the expected positions of the listener'sears. Typically, other speakers of the playback speaker array arenominally located in the floor plane.

When an audio object (e.g., the public address audio object of theprevious example) is determined by a discrete object channel of anobject based audio program, and corresponding metadata of the programindicates an above-floor source location (or trajectory of above-floorsource locations) from which the corresponding sound should be perceivedas emitting when the object channel is selected (and rendered andplayed), we refer to the audio object as an “above-floor” (or “height”)object, and to the object channel which indicates the above-floor objectas an “above-floor” (or “height”) object channel. An above-floor audioobject is typically rendered and played so that the resulting sound isemitted from at least one above-floor (or “height”) speaker of theplayback system speaker array.

If no above-floor (“height”) speaker is present in the playback systemspeaker array, a traditional downmixing technique (of the type mentionedabove) may be employed to downmix content of a selected “above-floor”object channel with content of speaker channels of the program (wherethe speaker channel content is intended to be played by floor speakersof the playback speaker array), so that the resulting downmixed sound isemitted only from floor speakers of the playback speaker array. However,because the content of the above-floor object channel would be downmixedinto the content of the speaker channels, the downmixing wouldundesirably result in a cacophonous-sounding mix (e.g., in which theabove-floor content would be perceived as interfering with originalspeaker channel content).

Using conditional rendering metadata included in an object-based audioprogram in accordance with some embodiments of the invention, arendering system can make intelligent decisions as to which audioobjects indicated by the program may or should be placed in whichspeaker channels of a downmix (and/or which audio objects should beomitted from which speaker channels of a downmix) of channels of theprogram, and at what volume each object should be downmixed with otheraudio content of the program, when a downmix of channels of the programis to be generated for playback by available speakers of the playbacksystem. Typical embodiments of the invention give sound mixers artisticflexibility to determine a good sounding mix (of content of an objectbased audio program) for each contemplated playback speaker arrayconfiguration without compromises that would otherwise result fromconventional downmixing, and to include corresponding conditionalrendering metadata in the to enable rendering of each such mix.

Conditional rendering of object channel content of an object based audioprogram in response to conditional rendering metadata included in theprogram (assuming knowledge of the available playback speaker arrayconfiguration), in accordance with typical embodiments of the invention,allows one or both of: automatic selection of a downmix rendering optionbased on a specific playback speaker array configuration (e.g., a settop box having a dedicated stereo output may be pre-configured so thatits object-based audio rendering engine always selects “stereo”conditional rendering metadata of an input object based program, anduses the selected “stereo” conditional rendering metadata to generatestereo speaker feeds in response to the program); and/or user selectionfrom among a menu of rendering options (e.g., downmix rendering options)available given a specific playback speaker array configuration. Forexample, the menu may include a small number of selectable downmixrendering options given that the playback speaker array consists only offloor speakers in a 5.1 channel configuration, including the followingoptions: a “home team commentary” downmix including content of a bed ofspeaker channels downmixed with a “home team commentary” object, an“away team commentary” downmix including content of a bed of speakerchannels downmixed with an “away team commentary” object, and a “hometeam commentary plus home team crowd noise” downmix including content ofa bed of speaker channels downmixed with a “home team commentary” objectand a “home team crowd noise” object.

For another example, the menu may include a larger number of selectabledownmix rendering options given that the playback speaker array consistsof floor speakers (e.g., in a 5.1 channel configuration) and a set ofheight (above-floor) speakers, including the following options: a “hometeam commentary” floor downmix including content of a bed of speakerchannels downmixed with a “home team commentary” object (for drivingonly floor speakers of the array), an “away team commentary” floordownmix including content of a bed of speaker channels downmixed with an“away team commentary” object (for driving only floor speakers of thearray), a “home team commentary plus home team crowd noise” floordownmix including content of a bed of speaker channels downmixed with a“home team commentary” object and a “home team crowd noise” object (fordriving only floor speakers of the array), and a “home team commentaryplus home team crowd noise plus public announcement” downmix includingcontent of a bed of speaker channels downmixed with a “home teamcommentary” object, a “home team crowd noise” object, and a publicannouncement object (for driving all speakers of the array, but withcontent of the public announcement object channel included only indownmix speaker feeds which drive above-floor speakers of the array, andall other content of the downmix included only in downmix speaker feedswhich drive floor speakers of the array).

The menu of rendering options (e.g., downmix rendering options) may bepresented to the user by a user interface of a controller, and thecontroller may be coupled to a set top device (or other device)configured to decode and render (at least partially) the object basedprogram. Metadata (included the above-noted conditional renderingmetadata) included in the program may allow user selection from among aset of options as to which object(s) indicated by the program should berendered, and as to how the object(s) to be rendered should beconfigured.

In some embodiments, the conditional rendering metadata specifies atleast the following attributes of each selectable downmix (of audiocontent of the program) selectable by a user (e.g., each selectabledownmix indicated by a menu of downmix rendering options), given theavailability of a playback speaker array having a specific correspondingconfiguration (of a set of possible playback speaker arrayconfigurations):

presence (i.e., for each object channel, an indication as to whether theobject channel should be present in the downmix for rendering by aplayback speaker array having the corresponding configuration);

position within soundfield (i.e., for each object channel to be includedin a downmix for rendering by a playback speaker array having thecorresponding configuration, an indication of apparent spatial locationfrom which the corresponding sound should be perceived as emitting whenspeaker feeds determined by the downmix drive the available speakers);

gain (i.e., for each object channel to be included in a downmix forrendering by a playback speaker array having the correspondingconfiguration, an indication of the gain to be applied to thecorresponding audio samples when generating the downmix); and

effects (i.e., for each object channel to be included in a downmix forrendering by a playback speaker array having the correspondingconfiguration, an indication each type of special effects processing (ifany) to be applied to the corresponding audio samples when generatingthe downmix. Examples of such processing include but are not limited todivergence processing and reverb application).

Another aspect of the invention is an audio processing unit (APU)configured to perform any embodiment of the inventive method. In anotherclass of embodiments, the invention is an APU including a buffer memory(buffer) which stores (e.g., in a non-transitory manner) at least oneframe or other segment (including audio content of speaker channels andat least one object channel, and object related metadata includingconditional rendering metadata) of an object based audio program whichhas been generated by any embodiment of the inventive method. Examplesof APUs include, but are not limited to encoders (e.g., transcoders),decoders, codecs, pre-processing systems (pre-processors),post-processing systems (post-processors), audio bitstream processingsystems, and combinations of such elements.

Aspects of the invention include a system or device configured (e.g.,programmed) to perform any embodiment of the inventive method, and acomputer readable medium (e.g., a disc) which stores code (e.g., in anon-transitory manner) for implementing any embodiment of the inventivemethod or steps thereof. For example, the inventive system can be orinclude a programmable general purpose processor, digital signalprocessor, or microprocessor, programmed with software or firmwareand/or otherwise configured to perform any of a variety of operations ondata, including an embodiment of the inventive method or steps thereof.Such a general purpose processor may be or include a computer systemincluding an input device, a memory, and processing circuitry programmed(and/or otherwise configured) to perform an embodiment of the inventivemethod (or steps thereof) in response to data asserted thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an AC-3 frame, including the segments into whichit is divided.

FIG. 2 is a diagram of the Synchronization Information (SI) segment ofan AC-3 frame, including segments into which it is divided.

FIG. 3 is a diagram of the Bitstream Information (BSI) segment of anAC-3 frame, including segments into which it is divided.

FIG. 4 is a diagram of an E-AC-3 frame, including segments into which itis divided.

FIG. 5 is a block diagram of an embodiment of a system, in which one ormore of the elements of the system may be configured in accordance withan embodiment of the invention.

FIG. 6 is a block diagram of a playback system which may be implementedto perform an embodiment of the inventive method.

FIG. 7 is a block diagram of a playback system which may be configuredto perform an embodiment of the inventive method.

FIG. 8 is a block diagram of a broadcast system configured to generatean object based audio program (and a corresponding video program) inaccordance with an embodiment of the invention.

FIG. 9 is a diagram of relationships between object channels of anembodiment of the inventive program, indicating which subsets of theobject channels are selectable by a user.

FIG. 10 is a block diagram of a system which may be implemented toperform an embodiment of the inventive method.

FIG. 11 is a diagram of content of an object based audio programgenerated in accordance with an embodiment of the invention.

NOTATION AND NOMENCLATURE

Throughout this disclosure, including in the claims, the expressionperforming an operation “on” a signal or data (e.g., filtering, scaling,transforming, or applying gain to, the signal or data) is used in abroad sense to denote performing the operation directly on the signal ordata, or on a processed version of the signal or data (e.g., on aversion of the signal that has undergone preliminary filtering orpre-processing prior to performance of the operation thereon).

Throughout this disclosure including in the claims, the expression“system” is used in a broad sense to denote a device, system, orsubsystem. For example, a subsystem that implements a decoder may bereferred to as a decoder system, and a system including such a subsystem(e.g., a system that generates X output signals in response to multipleinputs, in which the subsystem generates M of the inputs and the otherX-M inputs are received from an external source) may also be referred toas a decoder system.

Throughout this disclosure including in the claims, the term “processor”is used in a broad sense to denote a system or device programmable orotherwise configurable (e.g., with software or firmware) to performoperations on data (e.g., audio, or video or other image data). Examplesof processors include a field-programmable gate array (or otherconfigurable integrated circuit or chip set), a digital signal processorprogrammed and/or otherwise configured to perform pipelined processingon audio or other sound data, a programmable general purpose processoror computer, and a programmable microprocessor chip or chip set.

Throughout this disclosure including in the claims, the expression“audio video receiver” (or “AVR”) denotes a receiver in a class ofconsumer electronics equipment used to control playback of audio andvideo content, for example in a home theater.

Throughout this disclosure including in the claims, the expression“soundbar” denotes a device which is a type of consumer electronicsequipment (typically installed in a home theater system), and whichincludes at least one speaker (typically, at least two speakers) and asubsystem for rendering audio for playback by each included speaker (orfor playback by each included speaker and at least one additionalspeaker external to the soundbar).

Throughout this disclosure including in the claims, the expressions“audio processor” and “audio processing unit” are used interchangeably,and in a broad sense, to denote a system configured to process audiodata. Examples of audio processing units include, but are not limited toencoders (e.g., transcoders), decoders, codecs, pre-processing systems,post-processing systems, and bitstream processing systems (sometimesreferred to as bitstream processing tools).

Throughout this disclosure including in the claims, the expression“metadata” (e.g., as in the expression “processing state metadata”)refers to separate and different data from corresponding audio data(audio content of a bitstream which also includes metadata). Metadata isassociated with audio data, and indicates at least one feature orcharacteristic of the audio data (e.g., what type(s) of processing havealready been performed, or should be performed, on the audio data, orthe trajectory of an object indicated by the audio data). Theassociation of the metadata with the audio data is time-synchronous.Thus, present (most recently received or updated) metadata may indicatethat the corresponding audio data contemporaneously has an indicatedfeature and/or comprises the results of an indicated type of audio dataprocessing.

Throughout this disclosure including in the claims, the term “couples”or “coupled” is used to mean either a direct or indirect connection.Thus, if a first device couples to a second device, that connection maybe through a direct connection, or through an indirect connection viaother devices and connections.

Throughout this disclosure including in the claims, the followingexpressions have the following definitions:

speaker and loudspeaker are used synonymously to denote anysound-emitting transducer. This definition includes loudspeakersimplemented as multiple transducers (e.g., woofer and tweeter);

speaker feed: an audio signal to be applied directly to a loudspeaker,or an audio signal that is to be applied to an amplifier and loudspeakerin series;

channel (or “audio channel”): a monophonic audio signal. Such a signalcan typically be rendered in such a way as to be equivalent toapplication of the signal directly to a loudspeaker at a desired ornominal position. The desired position can be static, as is typicallythe case with physical loudspeakers, or dynamic;

audio program: a set of one or more audio channels (at least one speakerchannel and/or at least one object channel) and optionally alsoassociated metadata (e.g., metadata that describes a desired spatialaudio presentation);

speaker channel (or “speaker-feed channel”): an audio channel that isassociated with a named loudspeaker (at a desired or nominal position),or with a named speaker zone within a defined speaker configuration. Aspeaker channel is rendered in such a way as to be equivalent toapplication of the audio signal directly to the named loudspeaker (atthe desired or nominal position) or to a speaker in the named speakerzone;

object channel: an audio channel indicative of sound emitted by an audiosource (sometimes referred to as an audio “object”). Typically, anobject channel determines a parametric audio source description (e.g.,metadata indicative of the parametric audio source description isincluded in or provided with the object channel). The source descriptionmay determine sound emitted by the source (as a function of time), theapparent position (e.g., 3D spatial coordinates) of the source as afunction of time, and optionally at least one additional parameter(e.g., apparent source size or width) characterizing the source;

object based audio program: an audio program comprising a set of one ormore object channels (and optionally also comprising at least onespeaker channel) and optionally also associated metadata (e.g., metadataindicative of a trajectory of an audio object which emits soundindicated by an object channel, or metadata otherwise indicative of adesired spatial audio presentation of sound indicated by an objectchannel, or metadata indicative of an identification of at least oneaudio object which is a source of sound indicated by an object channel);and

render: the process of converting an audio program into one or morespeaker feeds, or the process of converting an audio program into one ormore speaker feeds and converting the speaker feed(s) to sound using oneor more loudspeakers (in the latter case, the rendering is sometimesreferred to herein as rendering “by” the loudspeaker(s)). An audiochannel can be trivially rendered (“at” a desired position) by applyingthe signal directly to a physical loudspeaker at the desired position,or one or more audio channels can be rendered using one of a variety ofvirtualization techniques designed to be substantially equivalent (forthe listener) to such trivial rendering. In this latter case, each audiochannel may be converted to one or more speaker feeds to be applied toloudspeaker(s) in known locations, which are in general different fromthe desired position, such that sound emitted by the loudspeaker(s) inresponse to the feed(s) will be perceived as emitting from the desiredposition. Examples of such virtualization techniques include binauralrendering via headphones (e.g., using Dolby Headphone processing whichsimulates up to 7.1 channels of surround sound for the headphone wearer)and wave field synthesis.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

FIG. 5 is a block diagram of an example of an audio processing chain(audio data processing system), in which one or more of the elements ofthe system may be configured in accordance with an embodiment of thepresent invention. The system includes the followings elements, coupledtogether as shown: capture unit 1, production unit 3 (which includes anencoding subsystem), delivery subsystem 5, decoder 7, object processingsubsystem 9, controller 10, and rendering subsystem 11. In variations onthe system shown, one or more of the elements are omitted, or additionalaudio data processing units are included. Typically, elements 7, 9, 10,and 11 are, or are included in, a playback system (e.g., the end user'shome theater system).

Capture unit 1 is typically configured to generate PCM (time-domain)samples comprising audio content, and to output the PCM samples. Thesamples may be indicative of multiple streams of audio captured bymicrophones (e.g., at a sporting event or other spectator event).Production unit 3, typically operated by a broadcaster, is configured toaccept the PCM samples as input and to output an object based audioprogram indicative of the audio content. The program typically is orincludes an encoded (e.g., compressed) audio bitstream (sometimesreferred to herein as a “main mix”) indicative of at least some of theaudio content, and optionally also at least one additional bitstream orfile (sometimes referred to herein as a “side mix”) indicative of someof the audio content. The data of the encoded bitstream (and of eachgenerated side mix, if any is generated) that are indicative of theaudio content are sometimes referred to herein as “audio data.” If theencoding subsystem of production unit 3 is configured in accordance witha typical embodiment of the present invention, the object based audioprogram output from unit 3 is indicative of (i.e., includes) multiplespeaker channels (a “bed” of speaker channels and optionally alsoreplacement speaker channels) of audio data, multiple object channels ofaudio data, and object related metadata (including conditional renderingmetadata). The program may include a main mix which in turn includesaudio content indicative of a bed of speaker channels, replacementspeaker channels, audio content indicative of at least oneuser-selectable object channel (and optionally at least one other objectchannel), and metadata (including object related metadata associatedwith each object channel, which in turn includes conditional renderingmetadata for at least one object channel). The program may also includeat least one side mix which includes audio content indicative of atleast one other object channel (e.g., at least one user-selectableobject channel) and/or object related metadata. The object relatedmetadata of the program may include durable metadata (to be describedbelow). The program (e.g., the main mix thereof) may be indicative ofone or more sets of speaker channels. For example, the main mix may beindicative of two or more sets of speaker channels (e.g., a 5.1 channelneutral crowd noise bed, a 2.0 channel set of replacement speakerchannels indicative of home team crowd noise, and a 2.0 channel set ofreplacement speaker channels indicative of away team crowd noise),including at least one user-selectable set of replacement speakerchannels (which can be selected using the same user interface employedfor user selection of object channel content or configuration) and a bedof speaker channels (which will be rendered in the absence of userselection of other content of the program). The bed (which may bereferred to as a default bed) may be determined by data indicative ofconfiguration (e.g., the initial configuration) of the speaker set ofthe playback system, and optionally the user may select other audiocontent of the program to be rendered in place of the default bed.

The metadata of the program may be indicative of at least one (andtypically more than one) selectable predetermined mix of content of atleast one of the object channels and content of predetermined ones ofthe speaker channels of the bed and/or replacement speaker channels ofthe program, and may include rendering parameters for each said mix.

Delivery subsystem 5 of FIG. 5 is configured to store and/or transmit(e.g., broadcast) the program generated by unit 3 (e.g., main mix andeach side mix thereof, if any side mix is generated).

In some embodiments, subsystem 5 implements delivery of an object basedaudio program, in which audio objects (and at least some correspondingobject related metadata) and speaker channels of the program are sentover a broadcast system (in a main mix of the program, indicated by anaudio bitstream which is broadcast), and at least some metadata of theprogram (e.g., object related metadata indicative of constraints onrendering or mixing of object channels of the program) and/or at leastone object channel of the program, are delivered (as a “side mix” of themain mix) in another manner (e.g., the side mix is sent to a specificend user by an Internet Protocol or “IP” network). Alternatively, theend user's decoding and/or rendering system is preconfigured with atleast some object related metadata (e.g., metadata indicative ofconstraints on rendering or mixing of audio objects of an embodiment ofthe inventive object based audio program), and such object relatedmetadata is not broadcast or otherwise delivered (by subsystem 5) withthe corresponding object channels (either in a main mix or side mix ofthe object based audio program).

In some embodiments, timing and synchronization of portions or elementsof an object based audio program which are delivered over separate paths(e.g., a main mix which is broadcast over a broadcast system, andrelated metadata which are sent as a side mix over an IP network), isprovided by synchronization words (e.g., time codes) that are sent overall the delivery paths (e.g., in a main mix and each corresponding sidemix).

With reference again to FIG. 5, decoder 7 accepts (receives or reads)the program (or at least one bitstream or other element of the program)delivered by delivery subsystem 5, and decodes the program (or eachaccepted element thereof). In some embodiments of the invention, theprogram includes a main mix (an encoded bitstream, e.g., an AC-3 orE-AC-3 encoded bitstream) and at least one side mix of the main mix, anddecoder 7 receives and decodes the main mix (and optionally also atleast one side mix). Optionally, at least one side mix of the program(e.g., an object channel) which does not need to be decoded is deliveredby subsystem 5 directly to object processing subsystem 9. If decoder 7is configured in accordance with a typical embodiment of the presentinvention, the output of decoder 7 in typical operation includes thefollowing:

streams of audio samples indicative of the program's bed of speakerchannels (and typically also of replacement speaker channels of theprogram); and

streams of audio samples indicative of object channels (e.g.,user-selectable audio object channels) of the program and correspondingstreams of object related metadata (including conditional renderingmetadata).

Object processing subsystem 9 is coupled to receive (from decoder 7)decoded speaker channels, object channels, and object related metadata(including conditional rendering metadata) of the delivered program, andoptionally also at least one side mix (indicative of at least one otherobject channel) of the program. For example, subsystem 9 may receive(from decoder 7) audio samples of the program's speaker channels and ofat least one object channel of the program, and object related metadataof the program, and may also receive (from delivery subsystem 5) audiosamples of at least one other object channel of the program (which havenot undergone decoding in decoder 7).

Subsystem 9 is coupled and configured to output to rendering subsystem11 a selected subset of the full set of object channels indicated by theprogram, and corresponding object related metadata. The selected subsetof object channels may be determined at least in part by conditionalrendering metadata of the program. Subsystem 9 is typically alsoconfigured to pass through unchanged (to subsystem 11) the decodedspeaker channels from decoder 7, and may be configured to process atleast some of the object channels (and/or metadata) asserted thereto togenerate the object channels and metadata it asserts to subsystem 11.

The object channel selection performed by subsystem 9 is typicallydetermined by user selection(s) (as indicated by control data assertedto subsystem 9 from controller 10) and/or rules (e.g., indicative ofconditions and/or downmix constraints or other rendering constraintsdetermined by conditional rendering metadata of the program) whichsubsystem 9 has been programmed or otherwise configured (e.g., inresponse to conditional rendering metadata) to implement. Such rules maybe determined by conditional rendering metadata and/or other objectrelated metadata of the program and/or by other data (e.g., dataindicative of the capabilities and configuration of the playbacksystem's speaker array) asserted to subsystem 9 (e.g., from controller10 or another external source) and/or by preconfiguring (e.g.,programming) subsystem 9. In some embodiments, controller 10 (via a userinterface implemented by controller 10) provides (e.g., displays on atouch screen) to the user a menu or palette of selectable “preset” mixesof speaker channel content (i.e., content of bed speaker channels and/orreplacement speaker channels) and object channel content (objects). Theselectable preset mixes may be determined by object related metadata ofthe program and typically also by rules implemented by subsystem 9(e.g., rules determined by conditional rendering metadata of theprogram, and/or rules which subsystem 9 has been preconfigured toimplement). The user selects from among the selectable mixes by enteringcommands to controller 10 (e.g., by actuating a touch screen thereof),and in response, controller 10 asserts corresponding control data tosubsystem 9 to cause rendering of the corresponding content inaccordance with the invention.

Rendering subsystem 11 of FIG. 5 is configured to render the audiocontent determined by the output of subsystem 9, for playback byplayback speaker array 13 of the playback system. Subsystem 11 hasknowledge of (e.g., is provided with data indicative of) the playbackspeaker array configuration of array 13 (e.g., the number of speakers ofarray 13, the type (e.g., full range or subwoofer) of each speaker ofarray 13, and the nominal or assumed location (e.g., in or above theplane of the floor, or the plane of the assumed position of a listener'sears) of each speaker of array 13 in the playback environment).Subsystem 11 is configured to map, to the available speaker channels,the audio object(s) determined by the object channel(s) selected byobject processing subsystem 9 (e.g., default objects, and/oruser-selected objects which have been selected as a result of userinteraction using controller 10), using rendering parameters output fromsubsystem 9 (e.g., user-selected and/or default values of spatialposition and level) which are associated with each selected object. Atleast some of the rendering parameters are determined by the objectrelated metadata output from subsystem 9. Rendering system 11 alsoreceives the speaker channels passed through by subsystem 9. Typically,subsystem 11 is an intelligent mixer, and is configured to determinespeaker feeds for the available speakers of array 13 including bymapping one or more selected (e.g., default-selected) objects to each ofa number of individual speaker channels, and mixing the objects withspeaker channel content indicated by each corresponding speaker channelof the program (e.g., each speaker channel of the program's bed ofspeaker channels). Typically, subsystem 11 is configured to render adownmix (consisting of a set of N downmixed speaker channels, where N isa positive integer) of audio channels (e.g., speaker channels and atleast one object channel) asserted thereto from subsystem 9, generatingN speaker feeds from the downmixed speaker channels, and causing Nspeakers of playback speaker array 13 to emit sound by driving thespeakers with the speaker feeds, where the downmix is compliant with atleast one (e.g., each) downmixing constraint indicated by conditionalrendering metadata of the program whose content is rendered.

An object based audio program generated in accordance with typicalembodiments of the invention (e.g., by unit 3 of FIG. 5) may be rendered(e.g., by the playback subsystem of FIG. 5, or the FIG. 6 system) tocause sound indicative of downmixed content (e.g., of object channelsand/or speaker channels) of the program played by a playback speakerarray to be perceived as emitting from different apparent sourcelocations within the sound reproduction (playback) environment. For aninteractive presentation, objects determined by selected ones ofselectable object channels are rendered at locations (e.g., a set ofdifferent static locations, corresponding to different ones of a set ofselected objects) within the rendered soundfield, such that audiocontent of each selected object channel is rendered so as to beperceived as emitting from an apparent source location (or trajectory oflocations) determined by object related metadata corresponding to theselected object channel. For example, an immersive sound mix determinedfrom an object based audio program may indicate sound which is in turnindicative of a “public address” audio object (determined by a selectedobject channel of the program) so as to be perceived as emitting from anapparent source location above the assumed listener's position withinthe reproduction environment to give the listener (consumer) theexperience of being in a stadium while announcements are emitted from apublic address loudspeaker mounted above the listener. Such a publicaddress audio object may be selected for rendering and playback by aspeaker array comprising at least one above-floor speaker physicallylocated in a horizontal plane (sometimes referred to as an “above-floor”or “height” plane) above a “floor” plane, where the “floor” plane is ahorizontal plane which nominally includes the expected positions of thelistener's ears. Typically, other speakers of the playback speaker arrayare nominally located in the floor plane.

When an audio object (e.g., the public address audio object of theprevious example) is determined by a discrete object channel of anobject based audio program, and corresponding metadata of the programindicates an above-floor source location (or trajectory of above-floorsource locations) from which the corresponding sound should be perceivedas emitting when the object channel is selected (and rendered andplayed), we refer to the audio object as an “above-floor” (or “height”)object, and to the object channel which indicates the above-floor objectas an “above-floor” (or “height”) object channel. An above-floor audioobject is typically rendered and played so that the resulting sound isemitted from at least one above-floor (or “height”) speaker of theplayback system speaker array.

If no above-floor (“height”) speaker is present in the playback systemspeaker array, a traditional downmixing technique (of the type mentionedabove) may be employed to downmix content of a selected “above-floor”object channel with content of speaker channels of the program (wherethe speaker channel content is intended to be played by floor speakersof the playback speaker array), so that the resulting downmixed sound isemitted only from floor speakers of the playback speaker array. However,because the content of the above-floor object channel would be downmixedinto the content of the speaker channels, the downmixing wouldundesirably result in a cacophonous-sounding mix (e.g., in which theabove-floor content would be perceived as interfering with originalspeaker channel content).

In a class of embodiments, an object based audio program (e.g., anobject based program generated by unit 3 of FIG. 3) includes conditionalrendering metadata corresponding to at least one object channel (e.g.,an above-floor object channel) of the program. Thus, each audio objectindicated by each such object channel has corresponding conditionalrendering metadata. For example, in some embodiments an audio objecthaving corresponding conditional rendering metadata may be anabove-floor object. The conditional rendering metadata is object relatedmetadata indicative of at least one rendering constraint (e.g., at leastone downmixing constraint), based on playback speaker arrayconfiguration, which applies to each corresponding object channel (i.e.,each object channel corresponding to the conditional renderingmetadata). An example of such a downmixing constraint is a prohibitionagainst downmixing of a corresponding object channel when the playbackspeaker array configuration is of a specific type. A playback system(having knowledge that its playback speaker array is of this specifictype) may be configured (e.g., preconfigured, or configured in responseto metadata of the program) to operate in response to the conditionalrendering metadata by preventing implementation of any downmix of theobject channel into a speaker channel of the program. Another example ofsuch a downmixing constraint is an indication of at least onepermissible downmix (or type of downmix) including a correspondingobject channel when the playback speaker array configuration is of aspecific type.

In a third example, the conditional rendering metadata may indicate thata corresponding object channel is of a first type (e.g., the objectchannel is indicative of an above-floor object) and that when theplayback speaker array configuration is of a second type (e.g., when thearray includes no above-floor speaker) no object channel of the programwhich is of the first type may be downmixed into a speaker channelintended for driving any speaker of the playback speaker array. Assumingthat the program includes conditional rendering metadata of this type, aplayback system (e.g., the system of FIG. 6 or the playback subsystem ofFIG. 5) having knowledge that its playback speaker array is of thesecond type may be configured (e.g., preconfigured, or configured inresponse to metadata of the program) to operate in response to theconditional rendering metadata by recognizing that the object channel isof the first type and preventing implementation of any downmix of theobject channel into a speaker channel (specified by a user-selected mixof content of the program) intended for driving any speaker of theplayback speaker array. In this case, the playback system may beconfigured also to notify the user (e.g., by displaying the notificationon a display screen of controller 10 of FIG. 5 or controller 23 of FIG.6) that the selected mix is unavailable. Also assuming that the programincludes conditional rendering metadata of this type, a playback system(having knowledge that its playback speaker array is not of the secondtype) may be configured to operate in response to the conditionalrendering metadata by recognizing that the object channel is of thefirst type and implementing a downmix of the object channel into aspeaker channel (specified by a user-selected mix, or default mix, ofcontent of the program) intended for driving a speaker of the playbackspeaker array.

Optionally, the conditional rendering metadata included in an objectbased audio program is also indicative of at least one rendering rule(e.g., at least one downmix rule), based on playback speaker arrayconfiguration, for rendering (e.g., implementing a downmix of) audiochannels of the program. For example, the conditional rendering metadatamay indicate the following downmix rules:

each object channel of the program of a first type (e.g., as indicatedby at least some conditional rendering metadata of the program) shouldbe downmixed into any speaker channel specified by any user-selected (ordefault) mix of content of the program if the playback speaker arrayincludes at least one above-floor speaker,

each object channel of the program of the first type should be ignored(i.e., should not be included in any downmix) by the playback system ifthe playback speaker array does not include at least one above-floorspeaker, and

each object channel of the program of a second type (e.g., as indicatedby at least some conditional rendering metadata of the program) shouldbe downmixed into any speaker channel specified by any user-selected (ordefault) mix of content of channels of the program regardless ofconfiguration of the playback speaker array.

In a class of embodiments, the invention is a method for generating anobject based audio program for playback by a speaker array (e.g.,playback speaker array 13 of FIG. 5), said method including steps of:

generating (e.g., in unit 3 of FIG. 5) conditional rendering metadatacorresponding to at least one object channel, such that the conditionalrendering metadata is indicative of at least one rendering constraint(e.g., at least one downmixing constraint), based on playback speakerarray configuration (e.g., configuration of playback speaker array 13),which applies to said at least one object channel;

determining (e.g., in unit 3 of FIG. 5) a set of audio channelsincluding said at least one object channel (and optionally also at leastone speaker channel); and

generating (e.g., in unit 3 of FIG. 5) the object based audio programsuch that said object based audio program is indicative of the set ofaudio channels and the conditional rendering metadata, and such thatcontent of at least one audio channel of the set of audio channels isrenderable, in a manner compliant with the at least one renderingconstraint, by a playback system in response to at least some of theconditional rendering metadata.

An example of a downmixing constraint indicated by the conditionalrendering metadata is a prohibition against downmixing of acorresponding object channel when the playback speaker arrayconfiguration is of a specific type. Another example of a renderingconstraint (which is a downmixing constraint) indicated by theconditional rendering metadata is an indication of at least onepermissible downmix (or type of downmix) including a correspondingobject channel when the playback speaker array configuration is of aspecific type. Optionally, the conditional rendering metadata is alsoindicative of at least one downmix rule, based on playback speaker arrayconfiguration, for implementing a downmix of audio channels of theprogram.

In other embodiments, the invention is a method of rendering audiocontent determined by an object based audio program, wherein the programis indicative of conditional rendering metadata corresponding to atleast one object channel, and a set of audio channels including the atleast one object channel (and optionally also at least one speakerchannel), and wherein the conditional rendering metadata is indicativeof at least one rendering constraint (e.g., at least one downmixingconstraint), based on playback speaker array configuration, whichapplies to said at least one object channel, said method including stepsof:

(a) providing the object based audio program to an audio processing unit(e.g., an audio processing unit which implements the playback subsystemof FIG. 5, which comprises decoder 7, object processing subsystem 9,controller 10, and rendering subsystem 11, or an audio processing unitwhich implements the FIG. 6 playback system); and

(b) in the audio processing unit (e.g., in decoder 7 of FIG. 5 ordecoder 20 of FIG. 6), parsing the conditional rendering metadata andthe set of audio channels, and rendering (e.g., in subsystems 9 and 11of FIG. 5 or subsystem 24 of FIG. 6) content of at least one audiochannel of the set of audio channels, in a manner compliant with the atleast one rendering constraint, in response to at least some of theconditional rendering metadata.

In some such embodiments, step (b) includes a step of selecting at leastone object channel of the set of audio channels (e.g., in subsystem 22of FIG. 6), and mixing (e.g., in subsystem 24 of FIG. 6) each selectedobject channel of the set with at least one speaker channel of the setto generate the downmix. Typically, the downmix consists of a set of Ndownmixed speaker channels, where N is a positive integer, and step (b)includes a step of causing N speakers of a playback speaker array toemit sound by driving the speakers with speaker feeds generated from thedownmixed speaker channels.

An example of a downmixing constraint indicated by the conditionalrendering metadata is a prohibition against downmixing of acorresponding object channel when the playback speaker arrayconfiguration is of a specific type. Another example of a downmixingconstraint indicated by the conditional rendering metadata is anindication of at least one permissible downmix (or type of downmix)including a corresponding object channel when the playback speaker arrayconfiguration is of a specific type. Optionally, the conditionalrendering metadata is also indicative of at least one rendering rule(e.g., at least one downmix rule), based on playback speaker arrayconfiguration, and the rendering performed in step (b) is compliant withthe rendering rule.

Table 1 below sets forth examples of audio object placement in downmixesbased on playback speaker array configuration, and enablement of typesof downmixing based on playback speaker array configuration, which maybe indicated by conditional rendering metadata in an object based audioprogram. In Table 1, the columns represent different audio objectchannels of (and thus audio objects indicated by) the program and therows indicate different playback speaker array configurations of aplayback system which performs the downmixing:

TABLE 1 Main Home Away Ambience Comm. Comm. Comm. P.A. Stereo L/R L/R5.1 5.1 Ls/Rs 5.1 + 4 height 5.1 + Height Ls/Rs Height

In the Table 1 example, the program is indicative of audio captured at asporting event in which two teams compete, and includes at least thefollowing object channels (as indicated in Table 1): an ambience channel(indicative of ambient content captured at the event); a main commentarychannel (“Main Comm.”) indicative of commentary which is not biased infavor of either team; a second commentary channel (“Home Comm.”)indicative of commentary biased in favor of the home team; a thirdcommentary channel (“Away Comm.”) indicative of commentary biased infavor of the away team; and a public announcement channel (“P.A.”)indicative of public address audio. The public address content of thepublic announcement channel is intended to be rendered by an above-floorspeaker of a playback speaker array (so that the resulting emitted soundis perceived as emitting from an apparent source location above theassumed listener's position). Each of the main commentary, secondcommentary, and third commentary channels is intended to be rendered byleft surround and right surround floor speakers of a playback speakerarray (so that each apparent source location from which the emittedsound is perceived to emit is nominally in the plane of the listener'sears). The ambience channel is intended to be rendered by all speakers(i.e., all available floor speakers and above-floor speakers) of aplayback speaker array.

In the example, the conditional rendering metadata indicates that whenthe playback speaker array is a stereo speaker array (consisting only ofa left (“L”) floor speaker and a right (“R”) floor speaker), theambience object channel and/or the main commentary object channel may bedownmixed with other audio content of the program (but not content ofthe public announcement channel) to generate left and right downmixchannels for driving the stereo speakers. The conditional renderingmetadata also indicates that when the playback speaker array is a stereospeaker array, the public announcement object channel should not bedownmixed with other audio content of the program (i.e., the conditionalrendering metadata establishes a rule preventing downmixing of contentof the public announcement object channel).

In the example, the conditional rendering metadata also indicates thatwhen the playback speaker array is a 5.1 speaker array (whose fullfrequency range speakers are left (“L”), center (“C”), right (“R”), leftsurround (“Ls”), and right surround (“Rs”) floor speakers), the maincommentary object channel may be downmixed with other audio content ofthe program (but not content of the public announcement channel) togenerate left surround and right surround downmix channels for drivingthe Ls and Rs floor speakers of the array. The conditional renderingmetadata also indicates that when the playback speaker array is a 5.1speaker array, the ambience object channel may be downmixed with otheraudio content of the program (but not content of the public announcementchannel) to generate left, right, center, left surround, and rightsurround downmix channels for driving the L, R, C, Ls, and Rs floorspeakers of the array. The conditional rendering metadata also indicatesthat when the playback speaker array is a 5.1 speaker array, the publicannouncement object channel should not be downmixed with other audiocontent of the program (i.e., the conditional rendering metadataestablishes a rule preventing downmixing of content of the publicannouncement object channel).

In the example, the conditional rendering metadata also indicates thatwhen the playback speaker array is a 5.1.4 speaker array (whose fullfrequency range speakers are left (“L”), center (“C”), right (“R”), leftsurround (“Ls”), and right surround (“Rs”) floor speakers, and four“height” speakers), the main commentary object channel may be downmixedwith other audio content of the program (but not content of the publicannouncement channel) to generate left surround and right surrounddownmix channels for driving the left surround and right surround floorspeakers. The conditional rendering metadata also indicates that whenthe playback speaker array is a 5.1.4 speaker array, the ambience objectchannel may be downmixed with other audio content of the program (butnot content of the public announcement channel) to generate left, right,center, left surround, right surround, and four height downmix channelsfor driving the L, R, C, Ls, and Rs floor speakers and the four heightspeakers of the array. The conditional rendering metadata also indicatesthat when the playback speaker array is a 5.1.4 speaker array, thepublic announcement object channel

should not be downmixed with other audio content of the program intofloor speaker downmix channels (i.e., the conditional rendering metadataestablishes a rule preventing downmixing of content of the publicannouncement object channel into floor channels of a downmix). Theconditional rendering metadata does not establish any rule preventingthe public announcement object channel from being downmixed with otheraudio content of the program (e.g., content of another height objectchannel) to generate height downmix channels for driving height speakersof a playback speaker array.

In accordance with typical embodiments of the invention, conditionalrendering of object channel content of an object based audio program inresponse to conditional rendering metadata included in the program(assuming knowledge of the available playback speaker arrayconfiguration) allows user selection from among a menu of renderingoptions (e.g., downmix rendering options) available given a specificplayback speaker array configuration. For example, the menu may includea small number of selectable downmix rendering options given that theplayback speaker array consists only of floor speakers in a 5.1 channelconfiguration, including the following options: a “home team commentary”downmix including content of a bed of speaker channels downmixed with a“home team commentary” object, an “away team commentary” downmixincluding content of a bed of speaker channels downmixed with an “awayteam commentary” object, and a “home team commentary plus home teamcrowd noise” downmix including content of a bed of speaker channelsdownmixed with a “home team commentary” object and a “home team crowdnoise” object.

For another example, the menu may include a larger number of selectabledownmix rendering options given that the playback speaker array consistsof floor speakers (e.g., in a 5.1 channel configuration) and a set ofheight (above-floor) speakers, including the following options: a “hometeam commentary” floor downmix including content of a bed of speakerchannels downmixed with a “home team commentary” object (for drivingonly floor speakers of the array), an “away team commentary” floordownmix including content of a bed of speaker channels downmixed with an“away team commentary” object (for driving only floor speakers of thearray), a “home team commentary plus home team crowd noise” floordownmix including content of a bed of speaker channels downmixed with a“home team commentary” object and a “home team crowd noise” object (fordriving only floor speakers of the array), and a “home team commentaryplus home team crowd noise plus public announcement” downmix includingcontent of a bed of speaker channels downmixed with a “home teamcommentary” object, a “home team crowd noise” object, and a publicannouncement object (for driving all speakers of the array, but withcontent of the public announcement object channel included only indownmix speaker feeds which drive above-floor speakers of the array, andall other content of the downmix included only in downmix speaker feedswhich drive floor speakers of the array).

The menu of rendering options may be presented to the user by a userinterface of a controller (e.g., a user interface implemented bycontroller 10 of FIG. 5 or controller 23 of FIG. 6), and the controllermay be coupled to a set top device (or other device) configured todecode and render (at least partially) the object based program.Metadata (including conditional rendering metadata) included in theprogram may allow user selection from among a set of options as to whichobject(s) indicated by the program should be rendered, and as to how theobject(s) to be rendered should be downmixed with other content of theprogram so that the resulting channels of downmixed content can berendered.

In some embodiments, the conditional rendering metadata specifies atleast the following attributes of each selectable downmix (of audiocontent of the program) selectable by a user (e.g., each selectabledownmix indicated by a menu of downmix rendering options), given theavailability of a playback speaker array having a specific correspondingconfiguration (of a set of possible playback speaker arrayconfigurations):

presence (i.e., for each object channel, an indication as to whether theobject channel should be present in the downmix for rendering by aplayback speaker array having the corresponding configuration);

position within soundfield (i.e., for each object channel to be includedin a downmix for rendering by a playback speaker array having thecorresponding configuration, an indication of apparent spatial locationfrom which the corresponding sound should be perceived as emitting whenspeaker feeds determined by the downmix drive the available speakers);

gain (i.e., for each object channel to be included in a downmix forrendering by a playback speaker array having the correspondingconfiguration, an indication of the gain to be applied to thecorresponding audio samples when generating the downmix); and

effects (i.e., for each object channel to be included in a downmix forrendering by a playback speaker array having the correspondingconfiguration, an indication each type of special effects processing (ifany) to be applied to the corresponding audio samples when generatingthe downmix. Examples of such processing include but are not limited todivergence processing and reverb application).

Aspects of embodiments of the invention include the following:

methods and systems for generating conditional rendering metadata (e.g.,in an authoring system or content creation facility) and including themetadata in an object based audio program (for example, some embodimentsof the inventive program generation system (e.g., unit 3 of FIG. 5) areprogrammed or otherwise configured to execute authoring software or tootherwise use authoring tools to define and generate conditionalrendering metadata for inclusion in an object based audio program); and

methods and systems (e.g., decoders and playback systems) for decodingan object based audio program (including by parsing conditionalrendering metadata of the program) and/or rendering content of an objectbased audio program (including by parsing conditional rendering metadataand performing downmixing of program content in accordance with theconditional rendering metadata).

In some embodiments, object related metadata (including conditionalrendering metadata) of an object based audio program includes (orconsists of) selectable content metadata indicative of a set ofselectable experience definitions. Each experience definition is aselectable, predetermined (“preset”) mix of audio content of the program(e.g., a mix of content of at least one object channel and at least onespeaker channel). Each preset mix has a predetermined set of renderingparameters (e.g., spatial locations of rendered objects). The presetmixes may be presented by a user interface of a playback system (e.g., auser interface implemented by controller 10 of FIG. 5 or controller 23of FIG. 6) as a limited menu or palette of available mixes. Optionally,object related metadata (including conditional rendering metadata) ofthe program includes metadata indicative of a layered mix graphindicative of selectable mixes (e.g., all selectable mixes) of speakerchannels and object channel(s) of the program.

FIG. 6 is a block diagram of an embodiment of a playback system whichincludes decoder 20, object processing subsystem 22, spatial renderingsubsystem 25, controller 23 (which implements a user interface), andoptionally also digital audio processing subsystems 25, 26, and 27,coupled as shown, and which can be implemented to perform embodiments ofthe inventive method. In some implementations, elements 20, 22, 24, 25,26, 27, 29, 31, and 33 of the FIG. 6 system are implemented as a set topdevice.

In the system of FIG. 6, decoder 20 is configured to receive and decodean encoded signal indicative of object based audio program (or of a mainmix of object based audio program). Typically, the program (e.g., theprogram's main mix) is indicative of audio content including a bed of atleast two speaker channels, at least one user-selectable object channel,and object related metadata (including conditional rendering metadata)corresponding to each object channel, in accordance with an embodimentof the invention. Each object channel is indicative of an audio object,and thus object channels are sometimes referred to herein as “objects”for convenience. In an embodiment, the program is (or includes main mixwhich is) an AC-3 or E-AC-3 bitstream, indicative of audio objects,object-related metadata (including conditional rendering metadata), abed of speaker channels, and optionally also selectable replacementspeaker channels. Typically, the individual audio objects are eithermono or stereo coded (i.e., each object channel is indicative of a leftor right channel of an object, or is a monophonic channel indicative ofan object), the bed is a traditional 5.1 mix, and decoder 20 may beconfigured to decode up to 16 channels of audio content (including thesix speaker channels of the bed, and replacement speaker channels andobject channels) simultaneously.

In some embodiments of the inventive playback system, each frame of anincoming E-AC-3 (or AC-3) encoded bitstream includes one or two metadata“containers.” The incoming bitstream is indicative of an object basedaudio program, or a main mix of such a program, and the speaker channelsof the program are organized as is the audio content of a conventionalE-AC-3 (or AC-3) bitstream. One container can be included in the Auxfield of the frame, and another container can be included in the addbsifield of the frame. Each container has a core header and includes (or isassociated with) one or more payloads. One such payload (of orassociated with a container included in the Aux field) may be a set ofaudio samples of each of one or more of the object channels (related toa bed of speaker channels which is also indicated by the program) andobject related metadata (including conditional rendering metadata)associated with each object channel. In such a payload, the samples ofsome or all of the object channels (and associated metadata) may beorganized as standard E-AC-3 (or AC-3) frames, or may be otherwiseorganized (e.g., they may be included in a side mix distinct from anE-AC-3 or AC-3 bitstream). An example of another such payload (of orassociated with a container included in either the addbsi field or theAux field) is a set of loudness processing state metadata associatedwith the audio content of the frame.

In some such embodiments, the decoder (e.g., decoder 20 of FIG. 6) wouldparse the core header of the container in the Aux field, and extract theinventive object channels and associated metadata from the container(e.g., from the Aux field of the AC-3 or E-AC-3 frame) and/or from thelocation (e.g., side mix) indicated by the core header. After extractingthe payload (object channels and associated metadata), the decoder wouldperform any necessary decoding on the extracted payload.

The core header of each container typically includes: at least one IDvalue indicating the type of payload(s) included in or associated withthe container; substream association indications (indicating whichsubstreams the core header is associated with); and protection bits.Such protection bits (which may consist of or include a hash-basedmessage authentication code or “HMAC”) would typically be useful for atleast one of decryption, authentication, or validation of object relatedmetadata (including conditional rendering metadata) and/or loudnessprocessing state metadata (and optionally also other metadata) includedin at least one payload included or associated with the container,and/or corresponding audio data included in the frame. Substreams may belocated “in band” (in the E-AC-3 or AC-3 bitstream) or “out of band”(e.g., in a side mix bitstream separate from the E-AC-3 or AC-3bitstream). One type of such payload is a set of audio samples of eachof one or more object channels (related to the bed of speaker channelswhich is also indicated by the program) and the object related metadataassociated with each object channel. Each object channel is a separatesubstream, and would typically be identified in the core header. Anothertype of payload is loudness processing state metadata.

Typically, each payload has its own header (or “payload identifier”).Object level metadata may be carried in each substream which is anobject channel. Program level metadata may be included in the coreheader of the container and/or in the header for a payload which is aset of audio samples of one or more object channels (and the metadataassociated with each object channel).

In some embodiments, each of the containers in the auxdata (or addbsi)field of the frame has three levels of structure:

a high level structure, including a flag indicating whether the auxdata(or addbsi) field includes metadata (where “metadata” in this contextdenotes object channels, object related metadata, and any other audiocontent or metadata which is carried by the bitstream but is notconventionally carried in a conventional E-AC-3 or AC-3 bitstream whichlacks any container of the type being described), at least one ID valueindicating what type(s) of metadata are present, and typically also avalue indicating how many bits of metadata (e.g., of each type) arepresent (if metadata is present). In this context, an example of onesuch “type” of metadata is object channel data and associated objectrelated metadata (i.e., a set of audio samples of each of one or moreobject channels (related to the bed of speaker channels also indicatedby the program) and the metadata associated with each object channel);

an intermediate level structure, comprising a core element for eachidentified type of metadata (e.g., core header, protection values, andpayload ID and payload size values, e.g., of the type mentioned above,for each identified type of metadata); and

a low level structure, comprising each payload for one core element ifat least one such payload is identified by the core element as beingpresent. An example of such a payload is a set of audio samples of eachof one or more object channels (related to the bed of speaker channelswhich is also indicated by the program) and metadata associated witheach object channel. Another example of such a payload is a payloadcomprising loudness processing state metadata (“LPSM”), sometimesreferred to as an LPSM payload.

The data values in such a three level structure can be nested. Forexample, the protection value(s) for a payload (e.g., an LPSM payload)identified by a core element can be included after each payloadidentified by the core element (and thus after the core header of thecore element). In one example, a core header could identify a firstpayload (e.g., an LPSM payload) and another payload, payload ID andpayload size values for the first payload could follow the core header,the first payload itself could follow the ID and size values, thepayload ID and payload size value for the second payload could followthe first payload, the second payload itself could follow these ID andsize values, and protection value(s) for either or both of the payloads(or for core element values and either or both of the payloads) couldfollow the last payload.

With reference again to FIG. 6, a user employs controller 23 to selectobjects (indicated by the object based audio program) to be rendered.Controller 23 may be a handheld processing device (e.g., an iPad) whichis programmed to implement a user interface (e.g., an iPad App)compatible with the other elements of the FIG. 6 system. The userinterface may provide (e.g., display on a touch screen) to the user amenu or palette of selectable “preset” mixes of objects, “bed” speakerchannel content, and replacement speaker channel content. The selectablepreset mixes may be determined by object related metadata (includingconditional rendering metadata) of the program and typically also byrules implemented by subsystem 22 (e.g., rules which subsystem 22 hasbeen preconfigured to implement) assuming knowledge by subsystem 22 ofthe configuration of the available playback speaker array. The userwould select from among the selectable mixes by entering commands tocontroller 23 (e.g., by actuating a touch screen thereof), and inresponse, controller 23 would assert corresponding control data tosubsystem 22.

In operation, decoder 20 decodes the speaker channels of the program'sbed of speaker channels (and any replacement speaker channels includedin the program), and outputs to subsystem 22 decoded speaker channels.In response to the object based audio program, and in response tocontrol data from controller 23 indicative of a selected subset of theprogram's full set of object channels to be rendered (including byundergoing downmixing), decoder 20 decodes (if necessary) the selectedobject channels, and outputs to subsystem 22 the selected (e.g.,decoded) object channels (each of which may be a pulse code modulated or“PCM” bitstream), and object related metadata corresponding to theselected object channels.

As well as the decoded speaker channels, decoded object channels, anddecoded object-related metadata from decoder 20, the inputs to objectprocessing subsystem 22 optionally include external audio objectchannels asserted (e.g., as one or more side mixes of a program whosemain mix is asserted to decoder 20) to the system. Examples of objectsindicated by such external audio object channels include a localcommenter (e.g., monophonic audio content delivered by a radio channel),an incoming Skype call, an incoming twitter connection (converted via atext-to-speech system, not shown in FIG. 6), and system sounds.

Subsystem 22 is configured to output a selected subset of the full setof object channels indicated by the program (or processed versions of aselected subset of the full set of object channels) and correspondingobject related metadata of the program, and a set of selected ones ofthe bed speaker channels and/or the replacement speaker channels. Theobject channel selection and speaker channel selection may be determinedby user selections (as indicated by control data asserted to subsystem22 from controller 23) and/or rules (e.g., indicative of conditionsand/or constraints) which subsystem 22 has been programmed or otherwiseconfigured to implement. Such rules may be determined by object relatedmetadata (including conditional rendering metadata) of the programand/or by other data (including data indicative of the configuration(e.g., capabilities and organization) of the playback system's speakerarray) asserted to subsystem 22 (e.g., from controller 23 or anotherexternal source) and/or by preconfiguring (e.g., programming) subsystem22. In some embodiments, object related metadata (including conditionalrendering metadata) of the program determines a set of selectable“preset” mixes of speaker channel content (of a bed of speaker channelsand/or replacement speaker channels) and objects, and subsystem 22 usesthis metadata to select the object channel(s) which it optionallyprocesses and then asserts to subsystem 24 and the speaker channelswhich it asserts to subsystem 24. Subsystem 22 typically passes throughunchanged (to subsystem 24) a selected subset of the decoded speakerchannels (bed speaker channels and typically also replacement speakerchannels) from decoder 20 (e.g., at least one speaker channel of a bedand at least one replacement speaker channel), and processes selectedones of the object channels asserted thereto.

The object processing (including object selection) performed bysubsystem 22 is typically controlled by control data from controller 23and object related metadata from decoder 20 (and optionally also objectrelated metadata of side mixes asserted to subsystem 22 other than fromdecoder 20), and typically includes determination of a spatial positionand a level for each selected object (regardless of whether the objectselection is due to user selection or selection by rule application).Typically, default spatial positions and default levels for renderingobjects, and restrictions on user selection of objects and their levels(in downmixed channels to be generated in subsystem 24) and spatialpositions (indicated by such downmixed channels), are included in orindicated by object related metadata (including conditional renderingmetadata) asserted (e.g., from decoder 20) to subsystem 22. Suchrestrictions may indicate forbidden combinations of objects (in adownmix) or forbidden spatial positions (indicated by downmixedchannels) with which selected objects may be rendered (e.g., to preventselected objects from being rendered too closely to each other, or toprevent specific objects from being included in downmixed channels forgenerating speaker feeds for driving the available playback speakerarray). In addition, the loudness of individual selected objects istypically controlled by object processing subsystem 22 in response tocontrol data entered using controller 23, and/or default levelsindicated by object related metadata (e.g., from decoder 20), and/or bypreconfiguration of subsystem 22.

Typically, the decoding performed by decoder 20 includes extraction(from the input program) of metadata indicating the type of audiocontent of each object indicated by the program (e.g., the type ofsporting event indicated by the program's audio content, and names orother identifying indicia (e.g., team logos) of selectable and defaultobjects indicated by the program). Controller 23 and object processingsubsystem 22 receive this metadata or relevant information indicated bythe metadata. Controller 23 also receives (e.g., is programmed with)information regarding the configuration of the user's playback speakerarray (e.g., the number of speakers, and an assumed placement or otherassumed organization of the speakers).

Spatial rendering subsystem 24 of FIG. 6 (or subsystem 24 with at leastone downstream device or system) is configured to render the audiocontent output from subsystem 22 for playback by speakers of the user'splayback speaker array. One or more of optionally included digital audioprocessing subsystems 25, 26, and 27 may implement post-processing onthe output of subsystem 24.

Spatial rendering subsystem 24 is configured to downmix, to theavailable speaker channels, speaker channel content (e.g., a selectedset of bed speaker channels and replacement speaker channels determinedby subsystem 22 and passed through subsystem 22 to subsystem 24) andcontent of each audio object channel selected (or selected andprocessed) by object processing subsystem 22 and asserted to subsystem24 (e.g., default-selected objects, and/or user-selected objects whichhave been selected as a result of user interaction using controller 23).The downmixing is accomplished using rendering parameters output fromsubsystem 22 (e.g., user-selected and/or default values of spatialposition and level) which are associated with each selected object.Typically, subsystem 24 is an intelligent mixer, and is configured todetermine speaker feeds for the available speakers including by mappingcontent of one, two, or more than two selected object channels to eachof a number of individual speaker channels, and performing downmixingwhich mixes the selected object channel(s) with audio content indicatedby each corresponding speaker channel.

In some implementations, the number of output (downmixed) speakerchannels may vary between 2.0 and 7.1, and the speakers to be driven torender the selected audio object channels (in a downmix with theselected speaker channel content) may be assumed to be located in a(nominally) horizontal plane in the playback environment. In such cases,the rendering is performed so that the speakers can be driven to emitsound that will be perceived as emitting from distinct object locationsin the plane of the speakers (i.e., one object location, or one sequenceof object locations along a trajectory, for each selected or defaultobject), mixed with sound determined by speaker channel content.

In various embodiments, the number of full range speakers to be drivento render the downmixed audio can be any number in a wide range (it isnot necessarily limited to be in the range from 2 to 7), and thus thenumber of output speaker channels is not limited to be in the range from2.0 and 7.1.

In some embodiments, the speakers to be driven to render the downmixedaudio are assumed to be located in arbitrary locations in the playbackenvironment; not merely in a (nominally) horizontal plane. In some suchcases, metadata included in the program indicates rendering parametersfor rendering at least one object of the program at any apparent spatiallocation (in a three dimensional volume) using a three-dimensional arrayof speakers. For example, an object channel may have correspondingmetadata indicating a three-dimensional trajectory of apparent spatialpositions at which the object (indicated by the object channel) is to berendered. The trajectory may include a sequence of “floor” locations (inthe plane of a subset of speakers which are assumed to be located in afloor plane of the playback environment), and a sequence of“above-floor” locations (each determined by driving a subset of thespeakers which are assumed to be located in at least one otherhorizontal plane of the playback environment). In such cases, therendering can be performed in accordance with the present invention sothat the speakers can be driven to emit sound (determined by therelevant object channel) that will be perceived as emitting from asequence of object locations in the three-dimensional space whichincludes the trajectory, mixed with sound determined by speaker channelcontent. Subsystem 24 may be configured to implement such rendering, orsteps thereof, with remaining steps of the rendering being performed bya downstream system or device (e.g., rendering subsystem 35 of FIG. 6).

Optionally, a digital audio processing (DAP) stage (e.g., one for eachof a number of predetermined output (downmixed) speaker channelconfigurations) is coupled to the output of spatial rendering subsystem24 to perform post-processing on the output of the spatial renderingsubsystem. Examples of such processing include intelligent equalizationor (in case of a stereo output) speaker virtualization processing.

The output of the FIG. 6 system (e.g., the output of the spatialrendering subsystem, or a DAP stage following the spatial renderingstage) may be PCM bitstreams (which determine speaker feeds for theavailable speakers). For example, in the case that the user's playbacksystem includes a 7.1 array of speakers, the system may output PCMbitstreams (generated in subsystem 24) which determine speaker feeds forthe speakers of such array, or a post-processed version (generated inDAP 25) of such bitstreams. For another example, in the case that theuser's playback system includes a 5.1 array of speakers, the system mayoutput PCM bitstreams (generated in subsystem 24) which determinespeaker feeds for the speakers of such array, or a post-processedversion (generated in DAP 26) of such bitstreams. For another example,in the case that the user's playback system includes only left and rightspeakers, the system may output PCM bitstreams (generated in subsystem24) which determine speaker feeds for the left and right speakers, or apost-processed version (generated in DAP 27) of such bitstreams.

The FIG. 6 system optionally also includes one or both of re-encodingsubsystems 31 and 33. Re-encoding subsystem 31 is configured tore-encode the PCM bitstream (indicative of feeds for a 7.1 speakerarray) output from DAP 25 as an E-AC-3 encoded bitstream, and theresulting encoded (compressed) E-AC-3 bitstream may be output from thesystem. Re-encoding subsystem 33 is configured to re-encode the PCMbitstream (indicative of feeds for a 5.1 speaker array) output from DAP27 as an AC-3 or E-AC-3 encoded bitstream, and the resulting encoded(compressed) AC-3 or E-AC-3 bitstream may be output from the system.

The FIG. 6 system optionally also includes re-encoding (or formatting)subsystem 29 and downstream rendering subsystem 35 coupled to receivethe output of subsystem 29. Subsystem 29 is coupled to receive data(output from subsystem 22) indicative of the selected audio objects (ordefault mix of audio objects), corresponding object related metadata,and the decoded speaker channels (e.g., bed speaker channels andreplacement speaker channels), and is configured to re-encode (and/orformat) such data for rendering by subsystem 35. Subsystem 35, which maybe implemented in an AVR or soundbar (or other system or devicedownstream from subsystem 29), is configured to generate speaker feeds(or bitstreams which determine speaker feeds) for the available playbackspeakers (speaker array 36), in response to the output of subsystem 29.For example, subsystem 29 may be configured to generate encoded audio,by re-encoding the data indicative of the selected (or default) audioobjects, corresponding metadata (including conditional renderingmetadata), and speaker channels, into a suitable format for rendering insubsystem 35, and to transmit the encoded audio (e.g., via an HDMI link)to subsystem 35. In response to speaker feeds generated by (ordetermined by the output of) subsystem 35, the available speakers 36would emit sound indicative of a mix of the speaker channel content andthe selected (or default) object(s), with the object(s) having apparentsource location(s) determined by object related metadata of subsystem29's output. When subsystems 29 and 35 are included, rendering subsystem24 is optionally omitted from the system.

In some embodiments, the invention is a distributed system for renderingobject based audio, in which a portion (i.e., at least one step) of therendering (e.g., selection of audio objects to be rendered and selectionof characteristics of the rendering of each selected object, asperformed by subsystem 22 and controller 23 of the FIG. 6 system) isimplemented in a first subsystem (e.g., elements 20, 22, and 23 of FIG.6, implemented in a set top device, or a set top device and a handheldcontroller) and another portion of the rendering (e.g., immersiverendering in which speaker feeds, or signals which determine speakerfeeds, are generated in response to the output of the first subsystem)is implemented in a second subsystem (e.g., subsystem 35, implemented inan AVR or soundbar). Some embodiments which provide distributedrendering also implement latency management to account for the differenttimes at which and different subsystems in which portions of the audiorender (and any processing of video which corresponds to the audio beingrendered) are performed.

In some embodiments of the inventive playback system, each decoder andobject processing subsystem (sometimes referred to as a personalizationengine) are implemented in a set top device (STB). For example, elements20 and 22 of FIG. 6, and/or all elements of the FIG. 7 system may beimplemented in an STB. In some embodiments of the inventive playbacksystem, multiple renderings are performed on the output of thepersonalization engine to ensure that all STB outputs (e.g., HDMI,S/PDIF, and stereo analog outputs of the STB) are enabled. Optionally,selected object channels (and corresponding object related metadata) andspeaker channels are passed on (with the decoded bed of speakerchannels) from the STB to a downstream device (e.g., an AVR or soundbar)configured to render a mix of the object channels and the speakerchannels.

In a class of embodiments, the inventive object based audio programincludes a set of bitstreams (multiple bitstreams, which may be referredto as “substreams”) which are generated and transmitted in parallel. Insome embodiments in this class, multiple decoders are employed to decodecontent of the substreams (e.g., the program includes multiple E-AC-3substreams and the playback system employs multiple E-AC-3 decoders todecode content of the substreams). FIG. 7 is a block diagram of aplayback system configured to decode and render an embodiment of theinventive object based audio program which comprises multiple serialbitstreams which are delivered in parallel.

The playback system of FIG. 7 is a variation on the FIG. 6 system inwhich the object based audio program includes multiple bitstreams (B1,B2, . . . , BN, where N is some positive integer) which are delivered tothe playback system in parallel and received by the playback system.Each of bitstreams (“substreams”) B1, B2, . . . , and BN is a serialbitstream which includes time codes or other synchronization words(referred to as “sync words” for convenience with reference to FIG. 7)to allow the substreams to be synchronized or time aligned with eachother. Each substream also includes a different subset of a full set ofobject channels and corresponding object related metadata, and at leastone of the substreams includes speaker channels (e.g., bed speakerchannels and replacement speaker channels). For example, in each ofsubstreams B1, B2, . . . , BN, each container which includes objectchannel content and object related metadata includes a unique ID or timestamp.

The FIG. 7 system includes N deformatters 50, 51, . . . , 53, eachcoupled and configured to parse a different one of the input substreams,and to assert the metadata (including the synch words thereof) and audiocontent thereof to bitstream synchronization stage 59.

Deformatter 50 is configured to parse substream B1, and to assert thesync words (T1) thereof, other metadata and object channel content (M1)thereof (including conditional rendering metadata and other objectrelated metadata, and at least one object channel of the program), andspeaker channel audio content (A1) thereof (including at least onespeaker channel of the program) to bitstream synchronization stage 59.Similarly, deformatter 51 is configured to parse substream B2, and toassert the sync words (T2) thereof, other metadata and object channelcontent (M2) thereof (including conditional rendering metadata and otherobject related metadata and at least one object channel of the program),and speaker channel audio content (A2) thereof (including at least onespeaker channel of the program) to bitstream synchronization stage 59.Similarly, deformatter 53 is configured to parse substream BN, and toassert the sync words (TN) thereof, other metadata and object channelcontent (MN) thereof (including conditional rendering metadata and otherobject related metadata and at least one object channel of the program),and speaker channel audio content (AN) thereof (including at least onespeaker channel of the program) to bitstream synchronization stage 59.

Bitstream synchronization stage 59 of the FIG. 7 system typicallyincludes buffers for the audio content and metadata of the substreamsB1, B2, . . . , BN, and a stream offset compensation element which iscoupled and configured to use the sync words of each of the substreamsto determine any misalignment of data in the input substreams (e.g.,which may occur due to the likelihood that tight synchronism among themis lost in distribution/contribution since each bitstream is typicallycarried over an independent interface and/or track within a media file).The stream offset compensation element of stage 59 is typically alsoconfigured to correct any determined misalignment by assertingappropriate control values to the buffers containing the audio data andmetadata of the bitstreams, to cause time-aligned bits of the speakerchannel audio data to be read from the buffers to decoders (includingdecoders 60, 61, and 63), each of which is coupled to a correspondingone of the buffers, and to cause time-aligned bits of the object channelaudio data and metadata to be read from the buffers to object datacombining stage 66.

Time-aligned bits of speaker channel audio content A1′ from substream B1are read from stage 59 to decoder 60, and time-aligned bits of objectchannel content and metadata M1′ from substream B1 are read from stage59 to metadata combiner 66. Decoder 60 is configured to perform decodingon the speaker channel audio data asserted thereto, and to assert theresulting decoded speaker channel audio to object processing andrendering subsystem 67.

Similarly, time-aligned bits of speaker channel audio content A2′ fromsubstream B2 are read from stage 59 to decoder 61, and time-aligned bitsof object channel content and metadata M2′ from substream B2 are readfrom stage 59 to metadata combiner 66. Decoder 61 is configured toperform decoding on the speaker channel audio data asserted thereto, andto assert the resulting decoded speaker channel audio to objectprocessing and rendering subsystem 67.

Similarly, time-aligned bits of speaker channel audio content AN′ fromsubstream BN are read from stage 59 to decoder 63, and time-aligned bitsof object channel content and metadata MN′ from substream BN are readfrom stage 59 to metadata combiner 66. Decoder 63 is configured toperform decoding on the speaker channel audio data asserted thereto, andto assert the resulting decoded speaker channel audio to objectprocessing and rendering subsystem 67.

For example, each of substreams B1, B2, . . . , BN may be an E-AC-3substream, and each of decoders 60, 61, 63, and any other decoder(s)coupled to subsystem 59 in parallel with decoders 60, 61, and 63, may bean E-AC-3 decoder configured to decode speaker channel content of one ofthe input E-AC-3 substreams.

Object data combiner 66 is configured to assert the time-aligned objectchannel data and metadata for all the object channels of the program inan appropriate format to object processing and rendering subsystem 67.

Subsystem 67 is coupled to the output of combiner 66 and to the outputsof decoders 60, 61, and 63 (and any other decoder(s) coupled in parallelwith decoders 60, 61, and 63 between subsystems 59 and 67), andcontroller 68 is coupled to subsystem 67. Subsystem 67 is typicallyconfigured to perform object processing on the outputs of combiner 66and the decoders (e.g., including the steps performed by subsystem 22 ofthe FIG. 6 system, or variations on such steps) in an interactive mannerin accordance with an embodiment of the invention, in response tocontrol data from controller 68. Controller 68 may be configured toperform the operations which controller 23 of the FIG. 6 system isconfigured to perform (or variations on such operations) in response toinput from a user. Subsystem 67 is typically also configured to performrendering on speaker channel audio and object channel audio dataasserted thereto (e.g., the operations performed by rendering subsystem24, or subsystems 24, 25, 26, 31, and 33 of the FIG. 6 system, orsubsystems 24, 25, 26, 31, 33, 29, and 35 of the FIG. 6 system, orvariations on such operations) in accordance with an embodiment of theinvention (e.g., to render a mix of bed speaker channel content,replacement speaker channel content, and object channel content).

In one implementation of the FIG. 7 system, each of substreams B1, B2, .. . , BN is a Dolby E bitstream. Each such Dolby E bitstream comprises asequence of bursts. Each burst may carry speaker channel audio content(content of bed speaker channels and/or replacement speaker channels)and a subset of a full object channel set (which may be a large set) ofthe inventive object channels and object related metadata (i.e., eachburst may indicate some object channels of the full object channel setand corresponding object related metadata including conditionalrendering metadata). Each burst of a Dolby E bitstream typicallyoccupies a time period equivalent to that of a corresponding videoframe. Each Dolby E bitstream in the set includes synchronization words(e.g., time codes) to allow the bitstreams in the set to be synchronizedor time aligned with each other. For example, in each bitstream, eachcontainer including object channel content and object related metadata(including conditional rendering metadata) could include a unique ID ortime stamp to allow the bitstreams in the set to be synchronized or timealigned with each other. In the noted implementation of the FIG. 7system, each of deformatters 50, 51, and 53 (and any otherdeformatter(s) coupled in parallel with deformatters 50, 51, and 53) isan SMPTE 337 deformatter, and each of decoders 60, 61, 63, and any otherdecoder(s) coupled to subsystem 59 in parallel with decoders 60, 61, and63, may be a Dolby E decoder.

In some embodiments of the invention, object related metadata of anobject based audio program includes durable metadata. For example, theobject related metadata included in the program input to subsystem 20 ofthe FIG. 6 system may include non-durable metadata (e.g., a defaultlevel and/or rendering position or trajectory, for a user-selectableobject) which can be changed at at least one point in the broadcastchain (from the content creation facility which generated the program tothe user interface implemented by controller 23) and durable metadatawhich is not intended to be changeable (or cannot be changed) afterinitial generation of the program (typically, in a content creationfacility). Examples of durable metadata include: conditional renderingmetadata for each user-selectable object or other object or set ofobjects of the program; an object ID for each user-selectable object orother object or set of objects of the program; and time codes or othersynchronization words indicative of timing of each user-selectableobject, or other object, relative to speaker channel content or otherelements of the program. Durable metadata is typically preservedthroughout the entire broadcast chain from content creation facility touser interface, throughout the entire duration of a broadcast of theprogram or even also during re-broadcasts of the program. In someembodiments, the audio content (and associated metadata) of at least oneuser-selectable object is sent in a main mix of the object based audioprogram, and at least some durable metadata (e.g., time codes) andoptionally also audio content (and associated metadata) of at least oneother object is sent in a side mix of the program.

Durable, object related metadata in some embodiments of the inventiveobject based audio program is employed to preserve (e.g., even afterbroadcast of the program) a user selected mix of object content andspeaker channel content. For example, this may provide the selected mixas a default mix each time the user a program of a specific type (e.g.,any soccer game) or each time the user watches any program (of anytype), until the user changes his/her selection. For example, duringbroadcast of a first program, the user may employ controller 23 (of theFIG. 6 system) to select a mix including an object having a durable ID(e.g., an object identified by controller 23's user interface as a “hometeam crowd noise” object, where the durable ID indicates “home teamcrowd noise”). Then, each time the user watches (and listens to) anotherprogram (which includes an object having the same durable ID), theplayback system will automatically render the program with the same mix(i.e., the bed speaker channels and/or replacement speaker channels ofthe program mixed with the program's “home team crowd noise” objectchannel), until the user changes the mix selection. Durable, objectrelated metadata in some embodiments of the inventive object based audioprogram may cause rendering of some objects to be mandatory (e.g.,despite a user desire to defeat such rendering) during an entireprogram.

In some embodiments, object related metadata provides a default mix ofobject content and speaker channel content, with default renderingparameters (e.g., default spatial locations of rendered objects). Forexample, the object related metadata of the program input to subsystem20 of the FIG. 6 system may be default mix of object content and speakerchannel content, with default rendering parameters, and subsystems 22and 24 will cause the program to be rendered with default mix, and withthe default rendering parameters, unless a user employs controller 23 toselect another mix of object content and speaker channel content and/oranother set of rendering parameters.

In some embodiments, object related metadata (including conditionalrendering metadata) provides a set of selectable “preset” mixes ofobjects and speaker channel content, each preset mix having apredetermined set of rendering parameters (e.g., spatial locations ofrendered objects). These may be presented by a user interface of theplayback system as a limited menu or palette of available mixes (e.g., alimited menu or palette displayed by controller 23 of the FIG. 6system). Each preset mix (and/or each selectable object) may have adurable ID (e.g., name, label or logo). Controller 23 (or the controllerof another embodiment of the inventive playback system) may beconfigured to display an indication of such ID (e.g., on the touchscreen of an iPad implementation of controller 23). For example, theremay be a selectable “home team” mix with an ID (e.g., a team logo) thatis durable, regardless of changes (e.g., made by the broadcaster) todetails of the audio content or nondurable metadata of each object ofthe preset mix.

In some embodiments, object related metadata of a program (or apreconfiguration of the playback or rendering system, not indicated bymetadata delivered with the program) provides constraints or conditionson selectable mixes of objects and bed (speaker channel) content. Forexample, an implementation of the FIG. 6 system may implement digitalrights management (DRM), and more specifically may implement a DRMhierarchy to allow a user of the FIG. 6 system to have “tiered” accessto a set of audio objects included in an object based audio program. Ifthe user (e.g., a customer associated with the playback system) paysmore money (e.g., to the broadcaster), the user may be authorized todecode and select (and hear) more audio objects of the program.

For another example, object related metadata may provide constraints onuser selection of objects. An example of such a constraint is that if auser employs controller 23 to select for rendering both a “home teamcrowd noise” object and a “home team announcer” object of a program(i.e., for inclusion in the mix determined by subsystem 24 of FIG. 6),metadata included in the program may ensure that subsystem 24 causes thetwo selected objects to be rendered with predetermined relative spatiallocations. The constraints may be determined (at least in part) by data(e.g., user-entered data) regarding the playback system. For example, ifthe playback system is a stereo system (including only two speakers),object processing subsystem 24 (and/or controller 23) of the FIG. 6system may be configured to prevent user selection of mixes (identifiedby object related metadata) that cannot be rendered with adequatespatial resolution by only two speakers. For another example, objectprocessing subsystem 24 (and/or controller 23) of the FIG. 6 system mayremove some delivered objects from the category of selectable objectsfor legal (e.g., DRM) reasons or other reasons (e.g. based on bandwidthof the delivery channel) indicated by object related metadata (and/orother data entered to the playback system). The user may pay the contentcreator or broadcaster for more bandwidth, and as a result the system(e.g., object processing subsystem 24 and/or controller 23 of the FIG. 6system) may allow the user to select from a larger menu of selectableobjects and/or object/bed mixes.

Some embodiments of the invention (e.g., implementations of the playbacksystem of FIG. 6 which include above-described elements 29 and 35)implement distributed rendering. For example, default or selected objectchannels (and corresponding object related metadata) of a program arepassed on (with decoded speaker channels, e.g., a selected set of bedspeaker channels and replacement speaker channels) from a set top device(e.g., from subsystems 22 and 29 of an implementation of the FIG. 6system) to a downstream device (e.g., subsystem 35 of FIG. 6,implemented in an AVR or soundbar downstream from the set top device(STB) in which subsystems 22 and 29 are implemented). The downstreamdevice is configured to render a mix of the object channels and speakerchannels. The STB may partially render the audio and the downstreamdevice may complete the rendering (e.g., by generating speaker feeds fordriving a specific top tier of speakers (e.g., ceiling speakers) toplace an audio object in a specific apparent source position, where theSTB's output merely indicates that the object can be rendered in someunspecified way in some unspecified top tier of speakers). For example,the STB may not have knowledge of the specific organization of thespeakers of the playback system, but the downstream device (e.g., AVR orsoundbar) may have such knowledge.

In some embodiments, the object based audio program (e.g., the programinput to subsystem 20 of the FIG. 6 system, or to elements 50, 51, and53 of the FIG. 7 system) is or includes at least one AC-3 (or E-AC-3)bitstream, and each container of the program which includes objectchannel content (and/or object related metadata including conditionalrendering metadata) is included in an auxdata field (e.g., the AUXsegment shown in FIG. 1 or FIG. 4) at the end of a frame of thebitstream. In some such embodiments, each frame of the AC-3 or E-AC-3bitstream includes one or two metadata containers. One container can beincluded in the Aux field of the frame, and another container can beincluded in the addbsi field of the frame. Each container has a coreheader and includes (or is associated with) one or more payloads. Onesuch payload (of or associated with a container included in the Auxfield) may be a set of audio samples of each of one or more of theinventive object channels (related to a bed of speaker channels which isalso indicated by the program) and the object related metadata(including conditional rendering metadata) associated with each objectchannel. The core header of each container typically includes at leastone ID value indicating the type of payload(s) included in or associatedwith the container; substream association indications (indicating whichsubstreams the core header is associated with); and protection bits.Typically, each payload has its own header (or “payload identifier”).Object level metadata may be carried in each substream which is anobject channel.

In other embodiments, the object based audio program (e.g., the programinput to subsystem 20 of the FIG. 6 system, or to elements 50, 51, and53 of the FIG. 7 system) is or includes a bitstream which is not an AC-3bitstream or an E-AC-3 bitstream. In some embodiments, the object basedaudio program is or includes at least one Dolby E bitstream, and theobject channel content and object related metadata of the program (e.g.,each container of the program which includes object channel contentand/or object related metadata including conditional rendering metadata)is included in bit locations of the Dolby E bitstream thatconventionally do not conventionally carry useful information. Eachburst of a Dolby E bitstream occupies a time period equivalent to thatof a corresponding video frame. The object channels (and/or objectrelated metadata) may be included in the guard bands between Dolby Ebursts and/or in the unused bit locations within each of data structures(each having the format of an AES3 frame) within each Dolby E burst. Forexample, each guard band consists of a sequence of segments (e.g., 100segments), each of the first X segments (e.g., X=20) of each guard bandincludes the object channels and object related metadata, and each ofthe remaining segments of said each guard band may include a guard bandsymbol. In some embodiments, at least some of the object channels(and/or object related metadata including conditional renderingmetadata) of the inventive program is included in the four leastsignificant bits (LSBs) of each of the two AES3 subframes of each of atleast some of the AES3 frames of a Dolby E bitstream, and the dataindicative of the program's speaker channels is included in the 20 mostsignificant bits (MSBs) of each of the two AES3 subframes of each AES3frame of the bitstream.

In some embodiments, the object channels and/or object related metadataof the inventive program are included in metadata containers in a DolbyE bitstream. Each container has a core header and includes (or isassociated with) one or more payloads. One such payload (of orassociated with a container included in the Aux field) may be a set ofaudio samples of each of one or more of the inventive object channels(e.g., related to a bed of speaker channels which is also indicated bythe program) and the object related metadata associated with each objectchannel. The core header of each container typically includes at leastone ID value indicating the type of payload(s) included in or associatedwith the container; substream association indications (indicating whichsubstreams the core header is associated with); and protection bits.Typically, each payload has its own header (or “payload identifier”).Object level metadata may be carried in each substream which is anobject channel.

In some embodiments, the object based audio program (e.g., the programinput to subsystem 20 of the FIG. 6 system, or to elements 50, 51, and53 of the FIG. 7 system) is decodable, and the speaker channel contentthereof is renderable, by a legacy decoder and legacy rendering system(which is not configured to parse the inventive object channels andobject related metadata). The same program may be rendered in accordancewith some embodiments of the invention by set top device (or otherdecoding and rendering system) which is configured (in accordance withan embodiment of the invention) to parse the inventive object channelsand object related metadata and render a mix of speaker channel andobject channel content indicated by the program.

Some embodiments of the invention are intended to provide a personalized(and preferably immersive) audio experience for end consumers inresponse to a broadcast program, and/or to provide new methods for usingmetadata in a broadcast pipeline. Some embodiments improve microphonecapture (e.g., stadium microphone capture) to generate audio programswhich provide a more personalizable and immersive experience for the endconsumer, modify existing production, contribution and distributionworkflows to allow object channel(s) and metadata of the inventiveobject based audio program(s) to flow through the professional chain,and create a new playback pipeline (e.g., one implemented in a set topdevice) that supports object channel(s), replacement speaker channels,and related metadata as well as conventionally broadcast audio (e.g.,the bed of speaker channels included in embodiments of the inventivebroadcast audio program).

FIG. 8 is a block diagram of a broadcast system configured to generatean object based audio program (and a corresponding video program) inaccordance with an embodiment of the invention, for broadcast. A set ofX microphones (where X is an integer), including microphones 100, 101,102, and 103, of the FIG. 8 system are positioned to capture audiocontent to be included in the program, and their outputs are coupled toinputs of audio console 104.

In a class of embodiments, the program includes interactive audiocontent which is indicative of the atmosphere in or at, and/orcommentary on a spectator event (e.g., a soccer or rugby game, a car ormotorcycle race, or another sporting event). In some embodiments, theaudio content of the program is indicative of multiple audio objects(including user-selectable objects or object sets, and typically also adefault set of objects to be rendered in the absence of object selectionby the user), a bed of speaker channels (indicative of a default mix ofcaptured content), and replacement speaker channels. The bed of speakerchannels may be a conventional mix (e.g., a 5.1 channel mix) of speakerchannels of a type that might be included in a conventional broadcastprogram which does not include an object channel.

In other embodiments, an object based audio program generated orrendered in accordance with the invention is indicative of “man-made”(e.g., digitally created) content rather than or as well as capturedaudio content. For example, the content may consist of or includenon-live (post-produced) content (e.g., synthesized audio).

A subset of the microphones (e.g., microphones 100 and 101 andoptionally also other microphones whose outputs are coupled to audioconsole 104) is a conventional array of microphones which, in operation,captures audio (to be encoded and delivered as a bed of speakerchannels, and a set of replacement speaker channels). In operation,another subset of the microphones (e.g., microphones 102 and 103 andoptionally also other microphones whose outputs are coupled to audioconsole 104) captures audio (e.g., crowd noise and/or other “objects”)to be encoded and delivered as object channels of the program. Forexample, the microphone array of the FIG. 8 system may include: at leastone microphone (e.g., microphone 100) implemented as a soundfieldmicrophone and permanently installed in a stadium (e.g., a soundfieldmicrophone having a heater installed with it); at least one stereomicrophone (e.g., microphone 102, implemented as a Sennheiser MKH416microphone or another stereo microphone) pointed at the location ofspectators who support one team (e.g., the home team), and at least oneother stereo microphone (e.g., microphone 103, implemented as aSennheiser MKH416 microphone or another stereo microphone) pointed atthe location of spectators who support the other team (e.g., thevisiting team).

The inventive broadcasting system may include a mobile unit (which maybe a truck, and is sometimes referred to as a “match truck”) locatedoutside of a stadium (or other event location), which is the firstrecipient of audio feeds from microphones in the stadium (or other eventlocation). The match truck generates the object based audio program (tobe broadcast) including by encoding audio content from microphones fordelivery as object channels of the program, generating correspondingconditional rendering metadata and other object related metadata (e.g.,metadata indicative of spatial location at which each object should berendered in a permitted downmix) and including such metadata in theprogram, and encoding audio content from some microphones for deliveryas a bed of speaker channels (and a set of replacement speaker channels)of the program.

For example, in the FIG. 8 system, console 104, object processingsubsystem 106 (coupled to the outputs of console 104), embeddingsubsystem 108, and contribution encoder 110 may be installed in a matchtruck. The object based audio program generated in subsystem 106 may becombined (e.g., in subsystem 108) with video content (e.g., from cameraspositioned in the stadium) to generate a combined audio and video signalwhich is then encoded (e.g., by encoder 110), thereby generating anencoded audio/video signal for broadcast (e.g., by delivery subsystem 5of FIG. 5). It should be understood that a playback system which decodesand renders such an encoded audio/video signal would include a subsystem(not specifically shown in the drawings) for parsing the audio contentand the video content of the delivered audio/video signal, and asubsystem (e.g., one similar or identical to the FIG. 6 system) fordecoding and rendering the audio content in accordance with anembodiment of the invention, and another subsystem (not specificallyshown in the drawings) for decoding and rendering the video content.

The audio output of console 104 may include a 5.1 speaker channel bed(labeled “5.1 neutral” in FIG. 8) indicative of a default mix of ambientsound captured at a sporting event, and commentary by an announcer(non-ambient content) mixed into its center channel, a replacementspeaker channel (labeled “1.0 replacement” in FIG. 8) indicative of theambient content of the center channel of the bed without the commentary(i.e., the captured ambient sound content of the bed's center channelbefore the commentary is mixed therewith to generate the bed's centerchannel), audio content of a stereo object channel (labeled “2.0 home”)indicative of crowd noise from the home team's fans who are present atthe event, audio content of a stereo object channel (labeled “2.0 away”)indicative of crowd noise from the visiting team's fans who are presentat the event, object channel audio content (labeled “1.0 comm1”)indicative of commentary by an announcer from the home team's city,object channel audio content (labeled “1.0 comm2”) indicative ofcommentary by an announcer from the visiting team's city, and objectchannel audio content (labeled “1.0 ball kick”) indicative of soundproduced by a game ball as it is struck by sporting event participants.

Object processing subsystem 106 is configured to organize (e.g., group)audio streams from console 104 into object channels (e.g., to group theleft and right audio streams labeled “2.0 away” into a visiting crowdnoise object channel) and/or sets of object channels, to generate objectrelated metadata indicative of the object channels (and/or objectchannel sets), and to encode the object channels (and/or object channelsets), object related metadata, the speaker channel bed, and eachreplacement speaker channel (determined from audio streams from console104) as an object based audio program (e.g., an object based audioprogram encoded as a Dolby E bitstream). Typically also, subsystem 106is configured to render (and play on a set of studio monitor speakers)at least a selected subset of the object channels (and/or object channelsets) and the speaker channel bed and/or replacement speaker channel(s)(including by using the object related metadata to generate a mixindicative of the selected object channel(s) and speaker channels) sothat the played back sound can be monitored by the operator(s) ofconsole 104 and subsystem 106 (as indicated by the “monitor path” ofFIG. 8).

The interface between subsystem 104's outputs and subsystem 106's inputsmay be a multichannel audio digital interface (“MADI”).

In operation, subsystem 108 of the FIG. 8 system combines the objectbased audio program generated in subsystem 106 with video content (e.g.,from cameras positioned in a stadium) to generate a combined audio andvideo signal which is asserted to encoder 110. The interface betweensubsystem 108's output and subsystem 110's input may be a highdefinition serial digital interface (“HD-SDI”). In operation, encoder110 encodes the output of subsystem 108, thereby generating an encodedaudio/video signal for broadcast (e.g., by delivery subsystem 5 of FIG.5).

In some embodiments, a broadcast facility is (e.g., subsystems 106, 108,and 110 of the FIG. 8 system are) configured to generate multiple objectbased audio programs (e.g., object based audio programs indicated bymultiple encoded audio/video signals output from subsystem 110 of FIG.8) indicative of captured sound. Examples of such object based audioprograms include a 5.1 flattened mix, an international mix, and adomestic mix. For example, all the programs may include a common bed ofspeaker channels (and a common set of replacement speaker channels), butthe object channels of the programs (and/or the menu of selectableobject channels determined by the programs, and/or selectable ornonselectable rendering parameters for rendering and mixing the objectchannels) may differ from program to program.

In some embodiments, a facility of a broadcaster or other contentcreator (e.g., subsystems 106, 108, and 110 of the FIG. 8 system) isconfigured to generate a single object based audio program (i.e., amaster) which can be rendered in any of a variety of different playbackenvironments (e.g., 5.1 channel domestic playback systems, 5.1 channelinternational playback systems, and stereo playback systems). The masterdoes not need to be mixed (e.g., downmixed) for broadcast to consumersin any specific environment.

As noted above, in some embodiments of the invention, object relatedmetadata of a program (or a preconfiguration of the playback orrendering system, not indicated by metadata delivered with the program)provides constraints or conditions on selectable mixes of objects andspeaker channel content. For example, an implementation of the FIG. 6system may implement a DRM hierarchy to allow a user to have tieredaccess to a set of object channels included in an object based audioprogram. If the user pays more money (e.g., to the broadcaster), theuser may be authorized to decode, select, and render more objectchannels of the program.

Examples of constraints and conditions on user selection of objects (orgroups of objects) will be described with reference to FIG. 9. In FIG.9, program “P0” includes seven object channels: object channel “NO”indicative of neutral crowd noise, object channel “N1” indicative ofhome crowd noise, object channel “N2” indicative of away crowd noise,object channel “N3” indicative of official commentary (e.g. broadcastcommentary by a commercial radio announcer) on an event, object channel“N4” indicative of fan commentary on the event, object channel “N5”indicative of public address announcements at the event, and objectchannel “N6” indicative of an incoming twitter connection (converted viaa text-to-speech system) pertaining to the event.

Default indicating metadata included in program P0 indicates a defaultobject set (one or more “default” objects) and default renderingparameter set (e.g., the spatial position of each default object in thedefault object set) to be included (by default) in a rendered mix of“bed” speaker channel content and object channel content indicated bythe program. For example, the default object set may be a mix of objectchannel “NO” (indicative of neutral crowd noise) rendered in a diffusemanner (e.g., so as not to be perceived as emitting from any specificsource location) and object channel “N3” (indicative of officialcommentary) rendered so as to be perceived as emitting from a sourcelocation directly in front of the listener (i.e., at an azimuth of 0degrees with respect to the listener).

Program P0 (of FIG. 9) also includes metadata indicating multiple setsof user selectable preset mixes, each preset mix determined by a subsetof the object channels of the program and a corresponding renderingparameter set. The user selectable preset mixes may be presented as amenu on a user interface of a controller of the playback system (e.g., amenu displayed by controller 23 of the FIG. 6 system). For example, onesuch preset mix is a mix of object channel “NO” of FIG. 9 (indicative ofneutral crowd noise) and object channel “N1” (indicative of home crowdnoise) and object channel “N4” (indicative of fan commentary), renderedso that the channel NO and N1 content in the mix is perceived asemitting from a source location directly behind the listener (i.e., atan azimuth of 180 degrees with respect to the listener), with the levelof channel N1 content in the mix being 3 dB less than the level ofchannel NO in the mix, and with the channel N4 content in the mixrendered in a diffuse manner (e.g., so as not to be perceived asemitting from any specific source location).

The playback system may implement a rule (e.g., a grouping rule “G”indicated in FIG. 9, determined by metadata of the program) that eachuser selectable preset mix that includes at least one of object channelsNO, N1, and N2 must include content of object channel NO alone, orcontent of object channel NO mixed with content of at least one ofobject channels N1 and N2. The playback system may also implement a rule(e.g., a condition rule “C1” indicated in FIG. 9, determined by metadataof the program) that each user selectable preset mix that includescontent of object channel NO mixed with content of at least one ofobject channels N1 and N2 must include content of object channel NOmixed with content of object channel N1, or it must include content ofobject channel NO mixed with content of object channel N2.

The playback system may also implement a rule (e.g., a condition rule“C2” indicated in FIG. 9, determined by metadata of the program) thateach user selectable preset mix that includes content of at least one ofobject channels N3 and N4 must include either content of object channelN3 alone, or it must include content of object channel N4 alone.

Some embodiments of the invention implement conditional decoding (and/orrendering) of object channels of an object based audio program. Forexample, the playback system may be configured to allow object channelsto be conditionally decoded based on conditional rendering metadataprovided with a program, and data indicative of playback speaker arrayconfiguration and optionally also the user's rights. For example, if aDRM hierarchy is implemented to allow customers to have “tiered” accessto a set of audio object channels included in an object based audioprogram, the playback system may be automatically configured (by controlbits included in metadata of the program) to prevent decoding andselection for rendering of some of the objects unless the playbacksystem is notified that the user has satisfied at least one condition(e.g., paying a specific amount of money to the content provider). Forexample, the user may need to purchase a right in order to listen to“official commentary” object channel N3 of program P0 of FIG. 9, and theplayback system may implement condition rule “C2” indicated in FIG. 9such that object channel N3 cannot be selected unless the playbacksystem is notified that the user of the playback system has purchasedthe necessary right.

For another example, the playback system may be automatically configured(by control bits included in metadata of the program, indicating aspecific configuration of the available playback speaker array) toprevent decoding and selection of some of the objects (for inclusion ina downmix of program content to be rendered) if the playback speakerarray configuration does not meet a condition (e.g., the playback systemmay implement condition rule “C1” indicated in FIG. 9 such that a presetmix of object channels NO and N1 cannot be selected unless the playbacksystem is notified that a 5.1 speaker array is available for renderingthe selected content, but not if the only available speaker array is a2.0 speaker array).

In some embodiments, the invention implements rule based object channelselection, in which at least one predetermined rule determines whichobject channel(s) of an object based audio program are rendered (e.g.,with a bed of speaker channels). The user may also specify at least onerule for object channel selection (e.g., by selecting from a menu ofavailable rules presented by a user interface of a playback systemcontroller), and the playback system (e.g., object processing subsystem22 of the FIG. 6 system) may be configured to apply each such rule todetermine which object channel(s) of an object based audio program to berendered should be included in the mix to be rendered (e.g., bysubsystem 24, or subsystems 24 and 35, of the FIG. 6 system). Theplayback system may determine from object related metadata (e.g.,conditional rendering metadata) in the program which object channel(s)of the program satisfy the predetermined rule(s) (e.g., given theconfiguration of the playback speaker array).

For a simple example, consider the case that the object based audioprogram is indicative of a sporting event. Instead of manipulating acontroller (e.g., controller 23 of FIG. 6) to perform static select of aspecific set of objects included in the program (e.g., radio commentaryfrom a specific team, or car, or bike), the user manipulates thecontroller to set up a rule (e.g., to automatically select, forrendering, object channels indicative of whatever team, or car, or bikeis winning or in first place). The rule is applied by the playbacksystem to implement dynamic selection (during rendering of a singleprogram, or a sequence of different programs) of a sequence of differentsubsets of the objects (object channels) included in the program (e.g.,a first subset of objects indicative of one team, automatically followedby a second subset of objects indicative of a second team upon the eventthat the second team makes a score and thus becomes the currentlywinning team). Thus, in some such embodiments, realtime events steer orinfluence which object channels are included in the rendered mix. Theplayback system (e.g., object processing subsystem 22 of the FIG. 6system) may respond to metadata included in the program (e.g., metadatawhich indicates that at least one corresponding object is indicative ofa currently winning team, e.g., is indicative of crowd noise of theteam's fans or commentary of a radio announcer associated with thewinning team) to select which object channel(s) should be included inthe mix of speaker and object channels to be rendered. For example, thecontent creator may include (in an object based audio program) metadataindicative of a place order (or other hierarchy) of each of at leastsome audio object channels of the program (e.g., indicative of whichobject channels correspond to the team or car currently in first place,which object channels correspond to the team or car in second place, andso on). The playback system may be configured to respond to suchmetadata by selecting and rendering only the object channel(s) whichsatisfy a user specified rule (e.g., the object channel(s) relating tothe team in “n” th place, as indicated by object related metadata of theprogram).

Examples of object related metadata regarding object channels of theinventive object based audio program include (but are not limited to):conditional rendering metadata or other metadata indicative of detailedinformation about how to render an object channel; dynamic temporalmetadata (e.g., indicative of a trajectory for panning of an object,object size, gains, etc.); and metadata for use by an AVR (or otherdevice or system downstream from decoding and object processingsubsystems of some implementations of the inventive system) to render anobject channel (e.g., with knowledge of the configuration of anavailable playback speaker array). Such metadata may specify constraintson object location, gain, muting, or other rendering parameters, and/orconstraints on how objects interact with other objects (e.g.,constraints on which additional objects may be selected given that aspecific object is selected), and/or may specify default objects and/ordefault rendering parameters (to be used in the absence of userselection of other objects and/or rendering parameters).

In some embodiments, at least some object related metadata (andoptionally also at least some of the object channels) of the inventiveobject based audio program are sent in a separate bitstream or othercontainer (e.g., as a side mix for which a user might need to pay extrato receive and/or use) from the program's bed of speaker channels andconventional metadata. Without access to such object related metadata(or object related metadata and object channels), a user could decodeand render the bed of speaker channels, but could not select audioobjects of the program and could not render audio objects of the programin a mix with the audio indicated by the speaker channel bed. Each frameof the inventive object based audio program may include audio content ofmultiple object channels and corresponding object related metadata.

An object based audio program generated (or transmitted, stored,buffered, decoded, rendered, or otherwise processed) in accordance withsome embodiments of the invention includes speaker channels, at leastone object channel, and metadata (including conditional renderingmetadata) indicative of a layered graph (sometimes referred to as alayered “mix graph”) indicative of selectable mixes (e.g., allselectable downmixes) of the speaker channels and object channel(s). Forexample, the mix graph is indicative of each rule applicable toselection of subsets of the speaker and object channels. Typically, anencoded audio bitstream is indicative of at least some (i.e., at least apart) of the program's audio content (e.g., a bed of speaker channelsand at least some of the program's object channels) and object relatedmetadata (including the metadata indicative of the mix graph), andoptionally also at least one additional encoded audio bitstream or fileis indicative of some of the program's audio content and/or objectrelated metadata.

The layered mix graph is indicative of nodes (each of which may beindicative of a selectable channel or set of channels, or a category ofselectable channels or set of channels) and connections between thenodes (e.g., control interfaces to the nodes and/or rules for selectingchannels), and includes essential data (a “base” layer) and optional(i.e., optionally omitted) data (at least one “extension” layer).Typically, the layered mix graph is included in one of the encoded audiobitstream(s) indicative of the program, and can be assessed by graphtraversal (implemented by a playback system, e.g., the end user'splayback system) to determine a default mix of channels and options formodifying the default mix.

Where the mix graph is representable as a tree graph, the base layer canbe a branch (or two or more branches) of the tree graph, and eachextension layer can be another branch (or another set of two or morebranches) of the tree graph. For example, one branch of the tree graph(indicated by the base layer) may be indicative of selectable channelsand sets of channels that are available to all end users, and anotherbranch of the tree graph (indicated by an extension layer) may beindicative of additional selectable channels and/or sets of channelsthat are available only to some end users (e.g., such an extension layermay be provided only to only end users authorized to use it). FIG. 9 isan example of a tree graph which includes object channel nodes (e.g.,nodes indicative of object channels NO, N1, N2, N3, N4, N5, and N6) andother elements of a mix graph.

Typically the base layer contains (is indicative of) the graph structureand control interfaces to the nodes of the graph (e.g., panning, andgain control interfaces). The base layer is necessary for mapping anyuser interaction to the decoding/rendering process.

Each extension layer contains (is indicative of) an extension to thebase layer. The extensions are not immediately necessary for mappinguser interaction to the decoding process and hence can be transmitted ata slower rate and/or delayed, or omitted.

In some embodiments, the base layer is included as metadata of anindependent substream of the program (e.g., is transmitted as metadataof the independent substream).

An object based audio program generated (or transmitted, stored,buffered, decoded, rendered, or otherwise processed) in accordance withsome embodiments of the invention includes speaker channels, at leastone object channel, and metadata (including conditional renderingmetadata) indicative of a mix graph (which may or may not be a layeredmix graph) indicative of selectable mixes (e.g., all selectabledownmixes) of the speaker channels and the object channel(s). An encodedaudio bitstream (e.g., a Dolby E or E-AC-3 bitstream) is indicative ofat least a portion of the program, and metadata indicative of the mixgraph (and typically also the selectable object and/or speaker channels)is included in every frame of the bitstream (or in each frame of asubset of the frames of the bitstream). For example, each frame mayinclude at least one metadata segment and at least one audio datasegment, and the mix graph may be included in at least one metadatasegment of each frame. Each metadata segment (which may be referred toas a “container”) may have a format which includes a metadata segmentheader (and optionally also other elements), and one or more metadatapayloads following the metadata segment header. Each metadata payload isitself identified by a payload header. The mix graph, if present in ametadata segment, is included in one of the metadata payloads of themetadata segment.

In another class of embodiments, an object based audio program generated(or transmitted, stored, buffered, decoded, rendered, or otherwiseprocessed) in accordance with the invention includes substreams, and thesubstreams are indicative of at least one bed of speaker channels, atleast one object channel, and object related metadata (includingconditional rendering metadata). The object related metadata includes“sub stream” metadata (indicative of substream structure of the programand/or the manner in which the substreams should be decoded) andtypically also a mix graph indicative of selectable mixes (e.g., allselectable downmixes) of the speaker channels and the object channel(s).The substream metadata may be indicative of which substreams of theprogram should be decoded independently of other substreams of theprogram, and which substreams of the program should be decoded inassociation with at least one other substream of the program.

For example, in some embodiments, an encoded audio bitstream isindicative of at least some (i.e., at least a part) of the program'saudio content (e.g., at least one bed of speaker channels, at least onereplacement speaker channel, and at least some of the program's objectchannels) and metadata (e.g., a mix graph and substream metadata, andoptionally also other metadata), and at least one additional encodedaudio bitstream (or file) is indicative of some of the program's audiocontent and/or metadata. In the case that each of the bitstreams is aDolby E bitstream (or is encoded in a manner consistent with the SMPTE337 format for carrying non-pcm data in an AES3 serial digital audiobitstream), the bitstreams can collectively be indicative of multiplesof up to 8 channels of audio content, with each bitstream carrying up to8 channels of audio data and typically also including metadata. Each ofthe bitstreams can be considered a substream of a combined bitstreamindicative of all the audio data and metadata carried by all thebitstreams.

For another example, in some embodiments, an encoded audio bitstream isindicative of multiple substreams of metadata (e.g., a mix graph andsubstream metadata, and optionally also other object related metadata)and audio content of at least one audio program. Typically, each of thesubstreams is indicative of one or more of the program's channels (andtypically also metadata). In some cases, multiple substreams of anencoded audio bitstream are indicative of audio content of several audioprograms, e.g., a “main” audio program (which may be a multichannelprogram) and at least one other audio program (e.g., a program which isa commentary on the main audio program).

An encoded audio bitstream which is indicative of at least one audioprogram necessarily includes at least one “independent” substream ofaudio content. The independent substream is indicative of at least onechannel of an audio program (e.g., the independent substream may beindicative of the five full range channels of a conventional 5.1 channelaudio program). Herein, this audio program is referred to as a “main”program.

In some cases, an encoded audio bitstream is indicative of two or moreaudio programs (a “main” program and at least one other audio program).In such cases, the bitstream includes two or more independentsubstreams: a first independent substream indicative of at least onechannel of the main program; and at least one other independentsubstream indicative of at least one channel of another audio program (aprogram distinct from the main program). Each independent bitstream canbe independently decoded, and a decoder could operate to decode only asubset (not all) of the independent substreams of an encoded bitstream.

Optionally, an encoded audio bitstream which is indicative of a mainprogram (and optionally also at least one other audio program) includesat least one “dependent” substream of audio content. Each dependentsubstream is associated with one independent substream of the bitstream,and is indicative of at least one additional channel of the program(e.g., the main program) whose content is indicated by the associatedindependent substream (i.e., the dependent substream is indicative of atleast one channel of a program which is not indicated by the associatedindependent substream, and the associated independent substream isindicative of at least one channel of the program).

In an example of an encoded bitstream which includes an independentsubstream (indicative of at least one channel of a main program), thebitstream also includes a dependent substream (associated with theindependent bitstream) which is indicative of one or more additionalspeaker channels of the main program. Such additional speaker channelsare additional to the main program channel(s) indicated by theindependent substream. For example, if the independent substream isindicative of standard format Left, Right, Center, Left Surround, RightSurround full range speaker channels of a 7.1 channel main program, thedependent substream may be indicative of the two other full rangespeaker channels of the main program.

In accordance with the E-AC-3 standard, a conventional E-AC-3 bitstreammust be indicative of at least one independent substream (e.g., a singleAC-3 bitstream), and may be indicative of up to eight independentsubstreams. Each independent substream of an E-AC-3 bitstream may beassociated with up to eight dependent substreams.

In an exemplary embodiment (to be described with reference to FIG. 11),an object based audio program includes at least one bed of speakerchannels, at least one object channel, and metadata. The metadataincludes “substream” metadata (indicative of substream structure ofaudio content of the program and/or the manner in which substreams ofaudio content of the program should be decoded) and typically also a mixgraph indicative of selectable mixes of the speaker channels and theobject channel(s). The audio program associated with a soccer game. Anencoded audio bitstream (e.g., an E-AC-3 bitstream) is indicative of theprogram's audio content and metadata. The audio content of the program(and thus of the bitstream) includes four independent substreams, asindicated in FIG. 11. One independent substream (labeled as substream“I0” in FIG. 11) is indicative of a 5.1 speaker channel bed indicativeof neutral crowd noise at the soccer game. Another independent substream(labeled as substream “I1” in FIG. 11) is indicative of a 2.0 channel“Team A” bed (“M crowd”) indicative of sound from the portion of thegame crowd biased toward one team (“Team A”), a 2.0 channel “Team B” bed(“LivP crowd”) indicative of sound from the portion of the game crowdbiased toward the other team (“Team B”), and a monophonic object channel(“Sky comm 1”) indicative of commentary on the game. A third independentsubstream (labeled as substream “I2” in FIG. 11) is indicative of objectchannel audio content (labeled “2/0 ball kick”) indicative of soundproduced by a game ball as it is struck by soccer game eventparticipants, and three object channels (“Sky comm 2,” “Man comm,” and“Liv Comm”) each indicative of a different commentary on the soccergame. The fourth independent substream (labeled as substream “I3” inFIG. 11) is indicative of an object channel (labeled “PA”) indicative ofsound produced by the stadium public address system at the soccer game,an object channel (labeled “Radio”) indicative of a radio broadcast ofthe soccer game, and an object channel (labeled “Goal Flash”) indicativeof scoring of a goal during the soccer game.

In the FIG. 11 example, substream I0 includes the mix graph for theprogram and metadata (“obj md”) including at least some of the substreammetadata and at least some object channel related metadata. Each ofsubstreams I1, I2, and I3 includes metadata (“obj md”) at least someobject channel related metadata and optionally at least some substreammetadata.

In the FIG. 11 example, substream metadata of the bitstream indicatesthat during decoding, coupling should be “off” between each pair of theindependent substreams (so that each independent substream is decodedindependently of the other independent substreams), and substreammetadata of the bitstream indicates the program channels within eachsubstream for which coupling should be “on” (so that these channels arenot decoded independently of each other) or “off” (so that thesechannels are decoded independently of each other). For example, thesubstream metadata indicates that coupling should be “on” internal toeach of the two stereo speaker channel beds (the 2.0 channel “Team A”bed and the 2.0 channel “Team B” bed) of substream I1 but disabledacross the speaker channel beds of substream I1 and between themonophonic object channel and each of the speaker channel beds ofsubstream I1 (to cause the monophonic object channel and the speakerchannel beds to be decoded independently of each other). Similarly, thesubstream metadata indicates that coupling should be “on” internal tothe 5.1 speaker channel bed of substream I0 (to cause the speakerchannels of this bed to be decoded in association with each other).

In some embodiments, speaker channels and object channels are included(“packed”) within substreams of an audio program in a manner appropriateto a mix graph of the program. For example, if the mix graph is a treegraph, all channels of one branch of the graph may be included withinone substream, and all channels of another branch of the graph may beincluded within another substream.

FIG. 10 is a block diagram of a system which implements an embodiment ofthe invention.

Object processing system (object processor) 200 of the FIG. 10 systemincludes metadata generation subsystem 210, mezzanine encoder 212, andemulation subsystem 211, coupled as shown. Metadata generation subsystem210 is coupled to receive captured audio streams (e.g., streamsindicative of sound captured by microphones positioned at a spectatorevent, and optionally also other audio streams), and configured toorganize (e.g., group) the audio streams from console 104 into a bed ofspeaker channels, a set of replacement speaker channels, and a number ofobject channels and/or sets of object channels. Subsystem 210 is alsoconfigured to generate object related metadata (including conditionalrendering metadata) indicative of the object channels (and/or objectchannel sets). Encoder 212 is configured to encode the object channels(and/or object channel sets), objected related metadata, and the speakerchannels as a mezzanine type object based audio program (e.g., an objectbased audio program encoded as a Dolby E bitstream).

Emulation subsystem 211 of object processor 200 is configured to render(and play on a set of studio monitor speakers) at least a selectedsubset of the object channels (and/or object channel sets) and thespeaker channels (including by using the object related metadata togenerate a mix indicative of the selected object channel(s) and speakerchannels) so that the played back sound can be monitored by theoperator(s) of subsystem 200.

Transcoder 202 of the FIG. 10 system includes mezzanine decodersubsystem (mezzanine decoder) 213, and encoder 214, coupled as shown.Mezzanine decoder 213 is coupled and configured to receive and decodethe mezzanine type object based audio program output from objectprocessor 200. The decoded output of decoder 213 is re-encoded byencoder 214 into a format suitable for broadcast. In one embodiment, theencoded object based audio program output from encoder 214 is an E-AC-3bitstream (and thus encoder 214 is labeled as “DD+Encoder” in FIG. 10).In other embodiments, the encoded object based audio program output fromencoder 214 is an AC-3 bitstream or has some other format. The objectbased audio program output of transcoder 202 is broadcast (or otherwisedelivered) to a number of end users.

Decoder 204 is included in the playback system of one such end user.Decoder 204 includes decoder 215 and rendering subsystem (renderer) 216,coupled as shown. Decoder 215 accepts (receives or reads) and decodesthe object based audio program delivered from transcoder 202. If decoder215 is configured in accordance with a typical embodiment of theinvention, the output of decoder 215 in typical operation includes:streams of audio samples indicative of the program's bed of speakerchannels, and streams of audio samples indicative of object channels(e.g., user-selectable audio object channels) of the program andcorresponding streams of object related metadata. In one embodiment, theencoded object based audio program input to decoder 215 is an E-AC-3bitstream, and thus decoder 215 is labeled as “DD+Decoder” in FIG. 10.

Renderer 216 of decoder 204 includes an object processing subsystemcoupled to receive (from decoder 215) decoded speaker channels, objectchannels, and object related metadata of the delivered program. Renderer216 also includes a rendering subsystem configured to render the audiocontent determined by the object processing subsystem, for playback byspeakers (not shown) of the playback system.

Typically, renderer 216's object processing subsystem is configured tooutput to renderer 216's rendering subsystem a selected subset of thefull set of object channels indicated by the program, and correspondingobject related metadata. Renderer 216's object processing subsystem istypically also configured to pass through unchanged (to the renderingsubsystem) the decoded speaker channels from decoder 215. The objectchannel selection performed by the object processing subsystem isdetermined in accordance with an embodiment of the invention, e.g., byuser selection(s) and/or rules (e.g., indicative of conditions and/orconstraints) which renderer 216 has been programmed or otherwiseconfigured to implement.

Each of elements 200, 202, and 204 of FIG. 10 (and each of elements 104,106, 108, and 110 of FIG. 8) may be implemented as a hardware system.The inputs of such a hardware implementation of processor 200 (orprocessor 106) would typically be multichannel audio digital interface(“MADI”) inputs. Typically, processor 106 of FIG. 8, and each ofencoders 212 and 214 of FIG. 10, includes a frame buffer. Typically, theframe buffer is a buffer memory coupled to receive an encoded inputaudio bitstream, and in operation the buffer memory stores (e.g., in anon-transitory manner) at least one frame of the encoded audiobitstream, and a sequence of the frames of the encoded audio bitstreamis asserted from the buffer memory to a downstream device or system.Also typically, each of decoders 213 and 215 of FIG. 10 includes a framebuffer. Typically, this frame buffer is a buffer memory coupled toreceive an encoded input audio bitstream, and in operation the buffermemory stores (e.g., in a non-transitory manner) at least one frame ofthe encoded audio bitstream to be decoded by decoder 213 or 215.

Any of the components or elements of processor 106 of FIG. 8 (orsubsystems 200, 202, and/or 204 of FIG. 10) may be implemented as one ormore processes and/or one or more circuits (e.g., ASICs, FPGAs, or otherintegrated circuits), in hardware, software, or a combination ofhardware and software.

It should be appreciated that in some embodiments, the inventive objectbased audio program is generated and/or delivered as an un-encoded(e.g., baseband) representation which is indicative of the programcontent (including metadata). For example, such representation cancomprise PCM audio samples and associated metadata. The un-encoded(uncompressed) representation can be delivered in any of a variety ofways, including as at least one file of data (e.g., stored in anon-transient manner in a memory, e.g., on computer-readable media), oras a bitstream in AES-3 format or in Serial Digital Interface (SDI)format (or in another format).

An aspect of the invention is an audio processing unit (APU) configuredto perform any embodiment of the inventive method. Examples of APUsinclude, but are not limited to encoders (e.g., transcoders), decoders,codecs, pre-processing systems (pre-processors), post-processing systems(post-processors), audio bitstream processing systems, and combinationsof such elements.

In a class of embodiments, the invention is an APU including a buffermemory (buffer) which stores (e.g., in a non-transitory manner) at leastone frame or other segment (including audio content of speaker channelsand of at least one object channel, and object related metadataincluding conditional rendering metadata) of an object based audioprogram which has been generated by any embodiment of the inventivemethod. For example, production unit 3 of FIG. 5 may include buffer 3A,which stores (e.g., in a non-transitory manner) at least one frame orother segment (including audio content of speaker channels and of atleast one object channel, and object related metadata includingconditional rendering metadata) of the object based audio programgenerated by unit 3. For another example, decoder 7 of FIG. 5 mayinclude buffer 7A, which stores (e.g., in a non-transitory manner) atleast one frame or other segment (including audio content of speakerchannels and of at least one object channel, and object related metadataincluding conditional rendering metadata) of the object based audioprogram delivered from subsystem 5 to decoder 7.

Embodiments of the present invention may be implemented in hardware,firmware, or software, or a combination thereof (e.g., as a programmablelogic array). For example, subsystem 106 of FIG. 8, or the FIG. 7system, or all or some of elements 20, 22, 24, 25, 26, 29, 35, 31, and35 of the FIG. 6 system, or all or some of elements 200, 202, and 204 ofFIG. 10, may be implemented in appropriately programmed (or otherwiseconfigured) hardware or firmware, e.g., as a programmed general purposeprocessor, digital signal processor, or microprocessor. Unless otherwisespecified, the algorithms or processes included as part of the inventionare not inherently related to any particular computer or otherapparatus. In particular, various general-purpose machines may be usedwith programs written in accordance with the teachings herein, or it maybe more convenient to construct more specialized apparatus (e.g.,integrated circuits) to perform the required method steps. Thus, theinvention may be implemented in one or more computer programs executingon one or more programmable computer systems (e.g., an implementation ofall or some of elements 20, 22, 24, 25, 26, 29, 35, 31, and 35 of FIG.6), each comprising at least one processor, at least one data storagesystem (including volatile and non-volatile memory and/or storageelements), at least one input device or port, and at least one outputdevice or port. Program code is applied to input data to perform thefunctions described herein and generate output information. The outputinformation is applied to one or more output devices, in known fashion.

Each such program may be implemented in any desired computer language(including machine, assembly, or high level procedural, logical, orobject oriented programming languages) to communicate with a computersystem. In any case, the language may be a compiled or interpretedlanguage.

For example, when implemented by computer software instructionsequences, various functions and steps of embodiments of the inventionmay be implemented by multithreaded software instruction sequencesrunning in suitable digital signal processing hardware, in which casethe various devices, steps, and functions of the embodiments maycorrespond to portions of the software instructions.

Each such computer program is preferably stored on or downloaded to astorage media or device (e.g., solid state memory or media, or magneticor optical media) readable by a general or special purpose programmablecomputer, for configuring and operating the computer when the storagemedia or device is read by the computer system to perform the proceduresdescribed herein. The inventive system may also be implemented as acomputer-readable storage medium, configured with (i.e., storing) acomputer program, where the storage medium so configured causes acomputer system to operate in a specific and predefined manner toperform the functions described herein.

A number of embodiments of the invention have been described. It shouldbe understood that various modifications may be made without departingfrom the spirit and scope of the invention. Numerous modifications andvariations of the present invention are possible in light of the aboveteachings. It is to be understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed herein.

What is claimed is:
 1. A method for generating an object based audioprogram, said method including steps of: generating conditionalrendering metadata corresponding to at least one object channel, suchthat the conditional rendering metadata is indicative of at least onerendering constraint, based on playback speaker array configuration,which applies to said at least one object channel, wherein theconditional rendering metadata is also indicative of at least onerendering rule, based on playback speaker array configuration, forrendering audio channels of the program, said at least one renderingrule including at least the following: each object channel of a firsttype should be downmixed into any speaker channel specified by anyuser-selected or default mix of content of the program if the playbackspeaker array includes at least one above-floor speaker, and each objectchannel of the first type should not be included in any downmix if theplayback speaker array does not include at least one above-floorspeaker; determining a set of audio channels including said at least oneobject channel; and generating the object based audio program such thatsaid object based audio program is indicative of the set of audiochannels and the conditional rendering metadata, and such that contentof at least one audio channel of the program is renderable, in a mannercompliant with the at least one rendering constraint, by a playbacksystem in response to at least some of the conditional renderingmetadata, where the playback speaker array includes at least one floorspeaker, each said floor speaker has an assumed location in a plane ofan assumed playback environment, the plane includes expected positionsof listener's ears in the playback environment, and each saidabove-floor speaker has an assumed location in the playback environmentabove said plane, and wherein the object based audio program is anencoded bitstream comprising frames, and each of at least some of theframes is indicative of at least one data structure which is a containerincluding some content of the at least one object channel and some ofthe conditional rendering metadata.
 2. The method of claim 1, whereinthe set of audio channels includes at least one speaker channel, andaudio content of at least one speaker channel of the set of audiochannels is indicative of sound captured at a spectator event, and audiocontent indicated by at least one object channel of the set of audiochannels is indicative of commentary on the spectator event.
 3. Themethod of claim 1, wherein the encoded bitstream is an AC-3 bitstream oran E-AC-3 bitstream, each of the frames of the encoded bitstream isindicative of at least one data structure which is a container includingsome content of the at least one object channel and some of theconditional rendering metadata, and at least one said container isincluded in an auxdata field or an addbsi field of each said frame. 4.The method of claim 1, wherein the object based audio program is a DolbyE bitstream comprising a sequence of bursts and guard bands betweenpairs of the bursts.
 5. A method of rendering audio content determinedby an object based audio program, wherein the program is indicative ofconditional rendering metadata corresponding to at least one objectchannel, and a set of audio channels including the at least one objectchannel, and wherein the conditional rendering metadata is indicative ofat least one rendering constraint, based on playback speaker arrayconfiguration, which applies to said at least one object channel,wherein the conditional rendering metadata is also indicative of atleast one rendering rule, based on playback speaker array configuration,for rendering audio channels of the program, and wherein the objectbased audio program is an encoded bitstream comprising frames, and eachof at least some of the frames is indicative of at least one datastructure which is a container including some content of the at leastone object channel and some of the conditional rendering metadata, saidmethod including steps of: (a) providing the object based audio programto an audio processing unit; and (b) in the audio processing unit,parsing the conditional rendering metadata and the set of audiochannels, and rendering content of at least one audio channel of the setof audio channels, in a manner compliant with the at least one renderingconstraint and the at least one rendering rule, in response to at leastsome of the conditional rendering metadata, wherein said at least onerendering rule includes at least the following: each object channel of afirst type should be downmixed into any speaker channel specified by anyuser-selected or default mix of content of the program if the playbackspeaker array includes at least one above-floor speaker, and each objectchannel of the first type should not be included in any downmix if theplayback speaker array does not include at least one above-floorspeaker, where the playback speaker array includes at least one floorspeaker, each said floor speaker has an assumed location in a plane ofan assumed playback environment, the plane includes expected positionsof listener's ears in the playback environment, and each saidabove-floor speaker has an assumed location in the playback environmentabove said plane.
 6. The method of claim 5, wherein the set of audiochannels includes at least one speaker channel, and step (b) includes astep of selecting at least one object channel of the set of audiochannels, thereby determining a selected object channel subset, andmixing each object channel of the selected object channel subset with atleast one speaker channel of the set to render a downmix of content ofthe selected object channel subset and said at least one speaker channelof the set.
 7. The method of claim 6, wherein step (b) includes stepsof: in response to at least some of the conditional rendering metadata,and based on a specific playback speaker array configuration of theaudio processing unit, providing a menu of rendering options which areavailable for selection; and selecting said at least one object channelof the set of audio channels, thereby determining the selected objectchannel subset, by selecting one of the rendering options indicated bythe menu.
 8. The method of claim 6, wherein the downmix consists of aset of N downmixed speaker channels, where N is a positive integer, andstep (b) includes a step of causing N speakers of a playback speakerarray to emit sound by driving the speakers with speaker feeds generatedfrom the downmixed speaker channels.
 9. The method of claim 7, whereinthe menu is presented by a user interface of a controller, thecontroller is coupled to a set top device, and the set top device iscoupled to receive the object based audio program and configured toperform step (b).
 10. A system for rendering audio content determined byan object based audio program, wherein the program is indicative ofconditional rendering metadata corresponding to at least one objectchannel, the program is also indicative of a set of audio channelsincluding the at least one object channel, and the conditional renderingmetadata is indicative of at least one rendering constraint, based onplayback speaker array configuration, which applies to said at least oneobject channel, wherein the conditional rendering metadata is alsoindicative of at least one rendering rule, based on playback speakerarray configuration, for rendering audio channels of the program, andwherein the object based audio program is an encoded bitstreamcomprising frames, and each of at least some of the frames is indicativeof at least one data structure which is a container including somecontent of the at least one object channel and some of the conditionalrendering metadata, said system including: a first subsystem coupled toreceive the object based audio program and configured to parse theconditional rendering metadata and the set of audio channels, and todetermine a selected subset of the set of audio channels; and arendering subsystem, coupled to the first subsystem and configured torender content indicated by the selected subset of the set of audiochannels, in a manner compliant with the at least one renderingconstraint and the at least one rendering rule, in response to at leastsome of the conditional rendering metadata, wherein said at least onerendering rule includes at least the following: each object channel of afirst type should be downmixed into any speaker channel specified by anyuser-selected or default mix of content of the program if the playbackspeaker array includes at least one above-floor speaker, and each objectchannel of the first type should not be included in any downmix if theplayback speaker array does not include at least one above-floorspeaker, where the playback speaker array includes at least one floorspeaker, each said floor speaker has an assumed location in a plane ofan assumed playback environment, the plane includes expected positionsof listener's ears in the playback environment, and each saidabove-floor speaker has an assumed location in the playback environmentabove said plane.
 11. The system of claim 10, wherein the set of audiochannels includes at least one speaker channel, and also including: acontroller coupled to the first subsystem, wherein the controller isconfigured to provide, in response to at least some of the conditionalrendering metadata and based on a specific playback speaker arrayconfiguration of system, a menu of rendering options which are availablefor selection, and wherein the controller is configured to determine theselected subset of the set of audio channels in response to userselection one of the rendering options indicated by the menu, andwherein the rendering subsystem is configured to mix each object channelof the selected subset of the set of audio channels with at least onespeaker channel of said selected subset of the set of audio channels torender the content.
 12. The system of claim 10, wherein the firstsubsystem is configured to select at least one object channel of the setof audio channels, thereby determining a selected object channel subset,and the rendering subsystem is configured to mix each object channel ofthe selected object channel subset with at least one speaker channel ofthe set to generate a downmix of content of the selected object channelsubset and said at least one speaker channel of the set.
 13. The systemof claim 12, wherein the downmix consists of a set of N downmixedspeaker channels, where N is a positive integer, and the renderingsubsystem is configured to generate speaker feeds from the downmixedspeaker channels for driving N speakers of a playback speaker array tocause said speakers to emit sound indicative of content of the downmix.